"The Science of Good Cooking"

Sauteed chicken breasts that turn out too dry, eggplant that's too oily.  Or tough and chewy roasts. Solving kitchen headaches like these has become a mission for the team at Cook's Illustrated magazine and PBS's America's Test Kitchen. Dozens of chefs experiment to create foolproof  recipes, and explain exactly why they work. 

Their latest project, The Science of Good Cooking, spells out the scientific principles behind some of their best recipes. Christopher Kimball, founder of Cook's Illustrated and host of America's Test Kitchen. joins us on Chicago Tonight at 7:00 pm. And watch the web-exclusive portion of our interview here.
Kimball's latest book revolves around 50 scientific principles, such as why marinating meat makes it taste better, with recipes based on those concepts and guides on relevant ingredients.
Below is a recipe for butter cookies and an explanation of the chemistry of butter : 

Glazed Butter Cookies

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The reverse creaming method—in which the butter is beaten into the flour and sugar rather than creamed with the sugar—makes for flatter cookies that are easier to decorate. Also, less air in the batter means fewer bubbles in the baked cookies, so they are sturdier and crisper—again, making them perfect for glazing.

Makes about 38 cookies

If you cannot find superfine sugar, process granulated sugar in a food processor for 30 seconds. If desired, the cookies can be finished with sprinkles or other decorations immediately after glazing.


            2 1/2  cups (121/2 ounces) all-purpose flour

            3/4      cup (52/3 ounces) superfine sugar

            1/4      teaspoon salt

            16        tablespoons unsalted butter, cut into 16 pieces and softened (68 degrees)

            2          tablespoons cream cheese, room temperature

            2          teaspoons vanilla extract



            1          tablespoon cream cheese, room temperature

            3          tablespoons milk

            1 1/2  cups (6 ounces) confectioners’ sugar


1. For the cookies: Using stand mixer fitted with paddle, mix flour, sugar, and salt at low speed until combined, about 5 seconds. With mixer running on low, add butter 1 piece at a time; continue to mix until mixture looks crumbly and slightly wet, 1 to 2 minutes longer. Beat in cream cheese and vanilla until dough just begins to form large clumps, about 30 seconds.

2. Knead dough by hand in bowl, 2 to 3 turns, until it forms large, cohesive mass. Transfer dough to counter and divide it into 2 even pieces. Press each piece into 4‑inch disk, wrap disks in plastic wrap, and refrigerate until dough is firm but malleable, about 30 minutes. (Dough can be refrigerated for up to 3 days or frozen for up to 2 weeks; defrost in refrigerator before using.)

3. Adjust oven rack to middle position and heat oven to 375 degrees. Line 2 baking sheets with parchment paper. Working with 1 piece of dough at a time, roll 1/8 inch thick between 2 large sheets of parchment paper; slide rolled dough, still on parchment, onto baking sheet and refrigerate until firm, about 10 minutes.

4. Working with 1 sheet of dough at a time, peel parchment from 1 side of dough and cut into desired shapes using cookie cutters; place cookies 11/2 inches apart on prepared sheets. Bake 1 sheet at a time until cookies are light golden brown, about 10 minutes, rotating baking sheet halfway through baking. (Dough scraps can be patted together, chilled, and rerolled once.) Let cookies cool on baking sheet for 3 minutes; transfer cookies to wire rack and let cool to room temperature.

5. For the glaze: Whisk cream cheese and 2 tablespoons milk together in medium bowl until combined and no lumps remain. Add confectioners’ sugar and whisk until smooth, adding remaining 1 tablespoon milk as needed until glaze is thin enough to spread easily. Using back of spoon, drizzle or spread scant teaspoon of glaze onto each cooled cookie. Allow glazed cookies to dry for at least 30 minutes.


Why This Recipe Works

Baking holiday cookies should be a fun endeavor, but so often it’s an exercise in frustration. The dough clings to the rolling pin, it rips and tears as it’s rolled out, and moving the dough in and out of the fridge to make it easier to work with turns a simple one-hour process into a half-day project. We wanted a simple recipe that would yield a forgiving, workable dough, producing cookies that would be sturdy enough to decorate yet tender enough to be worth eating. Our first realization was that we had to use enough butter to stay true to the nature of a butter cookie but not so much that the dough became greasy. All-purpose flour had enough gluten to provide structure, while superfine sugar provided a fine, even crumb and a compact, crisp cookie. A surprise ingredient—cream cheese—gave the cookies flavor and richness without altering their texture.

Use Superfine Sugar Regular granulated sugar makes cookies with a flaky texture and some large holes. In contrast, superfine sugar yields crisp, compact cookies with a fine, even crumb that is preferable for a cookie that will be glazed. There’s no leavener in these cookies (you want them flat) and no eggs (which would make them moist and chewy).

Add Cream Cheese We use just enough butter for rich flavor and tenderness. More butter just makes the dough sticky and hard to handle. However, we found that we could supplement the butter with cream cheese. Because it’s softer than butter when chilled it makes the dough easier to roll out. And it adds a nice tang.

Pick All-Purpose Flour While holiday glazed cookies should be delicate, cake flour makes overly fragile cookies. All-purpose flour develops enough gluten for cookies to be glazed and decorated without too much worry that they will crumble.

Roll, Then Chill To prevent the dough from sticking to the counter—and to the rolling pin—roll it between two large pieces of parchment. Cold, stiff dough will cut more cleanly than soft dough, so make sure to chill the dough after rolling. Slide the bottom piece of parchment onto a baking sheet to keep the dough flat and then refrigerate it until firm, about 10 minutes.

Minimize Scraps Cut shapes close together, starting from the outside and working your way to the middle. When making large and small cookies, alternate cutters as you stamp to use as much dough as possible. While you can reroll this dough once, you want to reduce scraps; if you overwork the dough too much gluten will develop and the cookies will bake up tough. Make sure to chill the dough scraps again before rolling them out a second time.

Peel Away Scraps First Use a small spatula to strip away the dough scraps from around the cookies. With excess dough out of the way, it’s easier to lift the cookies and transfer them to a baking sheet without marring the shape of the cookies, or stretching the dough.

Bake One Sheet at a Time Baking one sheet of cookies at a time ensures even baking. (For more on this, see “Avoiding Uneven Baking,” page 367.)



Butter 101


Fat: Globules of fat from cream or milk (some of them crystallized) stick together when churned, creating a larger mass, which is kneaded to make the bulk of butter. By law, fat must make up a minimum of 80 percent of the total content of butter. As a result of butter’s high level of ­saturated fat, it is a solid at room temperature, begins to melt at about 85 degrees, and is completely liquefied by 94 degrees. In its solid state, much of the fat occurs as tiny crystals surrounding the droplets of water along with a small amount of protein.

Water: Butter is 16 to 18 percent water. Butter is one of the few ingredients in the kitchen composed of a water-in-oil emulsion, which is an emulsion of tiny droplets of water suspended in a continuous phase of fat, similar to a classic vinaigrette (see concept 36). A small amount of protein coats the water droplets and keeps them from coalescing unless the butter is completely melted.

Milk Solids: “Milk solids” is the term used to describe everything in butter that isn’t water or fat. Milk solids are rich in protein, carbohydrates, vitamins, and minerals, which are all removed when clarifying butter, except for the fat-soluble vitamins. The milk solids represent about 1 percent of the compounds found in butter.


You have four basic decisions at the market—salted or unsalted, cultured or uncultured, regular or premium, and whipped or stick.

Salted or Unsalted? In the test kitchen, we use unsalted butter almost exclusively and add our own salt to recipes. Why? First, the amount of salt in salted butter varies from brand to brand—on average 1/3 -teaspoon a stick—which makes offering a universal conversion impossible. Second, salted butter almost always contains more water, which can influence gluten development—particularly important in baking. (Biscuits made with salted butter were noticeably mushy.) Third, salt overshadows butter’s naturally sweet, delicate flavors; in butter-specific recipes like beurre blanc and -buttercream frosting, we found that extra salt to be overwhelming.

Cultured or Uncultured? The real distinction between premium and regular butters (see description at right) is culturing—the process of fermenting the cream before churning it that builds tangy, complex flavors. Cultured butters are produced by adding certain strains of bacteria that produce unique flavors. That said, these nuances are subtle in most cooked applications, so we save the expensive cultured stuff for spreading on toast.

Whipped or Stick? Whipped butter, made by beating air into butter, makes a creamy spread but isn’t always a good alternative to stick butter for cooking. While testers couldn’t tell the difference in baked goods, they found the aerated butter “foamy” and “plasticlike” in uncooked applications such as frosting. If you want to use whipped butter, base your substitution on weight, not volume. (Adding air increases the volume, not the weight.) A standard tub of whipped butter weighs 8 ounces, equal to two sticks of butter.

Regular or Premium? While you hear a lot about the higher fat content in premium butters, our tasters had trouble telling the difference, even when tasted plain. Regular unsalted butter contains 81 to 82 percent fat; premium brands have 83 to 86 percent fat. Because higher-fat butter remains solid over a wider temperature range, we like it when making croissant dough and other recipes where rapid softening of the butter would cause problems. 


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