Holiday Cookies: the chemistry and math of making them. Plus, a recipe.

How the ball of dough flattens, spreads and bubbles in the oven?
Why tasting raw dough is like playing a Russian roulette?
Why your cookies won't brown at the standard 350F?
How could you figure out that they are ready without using a kitchen timer?

All the answers and much much more interesting details are in this TedEd video:



But wait, there is more:
When you use melted butter instead of the room temperature butter chunks, the dough will spread out faster in the oven creating larger diameter cookies. At the same time meted butter will create more but smaller sized air pockets (holes) making the cookies chewier. Source: molecular biologist Liz Roth-Johnson, UCLA.

And the biggest secret is to make the dough 3 days ahead and refrigerate it for about 36 hours prior to shaping and baking in order to allow all the ingredients slowly penetrate each other and achieve better dough consistency. More details on that are in this NYTimes article.

Finally, as we learned all the science, let's try making the cookies.
My friend and excellent baker Sherene Michlin recommended two of her favorite recipes. One that is adapted from NY baker Jacques Torres and requires two types of flour, two types of sugar and very precise measurements. NYTimes subscribers could find it here.
Another: basic, straight-forward, no-fail - is from the NESTLE website.  I am posting it below.

Ingredients:
2 1/4 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
1 cup (2 sticks) butter, softened
3/4 cup granulated sugar
3/4 cup packed brown sugar
1 teaspoon vanilla extract
2 large eggs
2 cups (12-oz. pkg) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels
1 cup chopped nuts

Directions:

preheat oven to 375° F.

combine flour, baking soda and salt in small bowl. Beat butter, granulated sugar, brown sugar and vanilla extract in large mixer bowl until creamy. Add eggs, one at a time, beating well after each addition. Gradually beat in flour mixture. Stir in morsels and nuts. Drop by rounded tablespoon onto ungreased baking sheets. 

bake for 9 to 11 minutes or until golden brown. Cool on baking sheets for 2 minutes; remove to wire racks to cool completely. 

Enjoy!

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