The Chemistry of Cookies

What makes this chocolate chip cookie recipe perfect? Let’s break it down.

Chemistry, cooking, cookies — all are a part of the recipe for Lesa Tran Lu ’07, assistant teaching professor, lecturer and associate director for educational programs at the Institute of Biosciences and Bioengineering at Rice. Tran, who earned a B.S., an M.A. and a Ph.D., all in chemistry at Rice, has employed an inquiry-based learning model since joining the faculty in 2012. Her popular Chemistry of Cooking class is hands-on and interactive. Lu educates by experimentation, teaching students the science behind recipes and how and why various ingredients mixed together work and other methods fail.

Photo of chocolate chip cookies and a glass of cold milk
Photo by Alese Pickering

Growing up in a family who owned a fortune cookie factory in Houston, Lu learned to cook at a very young age. She became intrigued by how chemistry and the science behind ingredients make or break a recipe. “Cookies are something that everyone relates to regardless of their cooking experience,” Lu said. “Experimenting with ratios and ingredients is fun, and a chocolate chip cookie recipe is low risk if it doesn’t work out.”  

What’s the perfect drink to accompany a hot-out-of-the-oven chocolate chip cookie? A cold glass of milk, of course.

A silicone mat is best for even and nonstick baking.

Pro tip: Chill the dough before baking. It flattens out less and gives the dough more time to develop the flavors of the ingredients.

Lu’s perfect chocolate chip cookie is crispy on the outside and thicker with a chewy, gooey, cakelike middle.

How many recipes did it take to make the perfect chocolate chip cookie? “Five or six,” said Lu. “It’s all about the fine-tuning and different ratios.”

This recipe uses both bread flour and all-purpose flour and three types of sugar.

Lu recommends Ghirardelli bitter-sweet chocolate chips because the chips are larger and flat and spread out in the cookie when they bake.

— Tracey Rhoades


The Perfect Chocolate Chip Cookie
by Lesa Tran Lu 


  • 1 cup (140 g) bread flour
  • ½ cup (70 g) all-purpose flour
  • ¾ tsp (5 g) salt
  • ½ teaspoon (2 g) baking powder
  • ½ teaspoon (3 g) baking soda
  • 8 tbsp (113 g) unsalted butter, at room temperature
  • ½ cup (100 g) granulated white sugar
  • ¼ cup packed (55 g) light brown sugar
  • ¼ cup packed (55 g) dark brown sugar
  • 1 large egg
  • ½ tsp (2 g) pure vanilla extract
  • 8 oz (226 g) bittersweet chocolate chips


In a medium bowl, whisk together the flours, salt, baking powder and baking soda. Set aside.

In the bowl of an electric mixer fitted with the paddle attachment, cream together the butter and sugars on medium-high speed until smooth, about 2 to 3 minutes. 

Add the egg and vanilla, and mix well. Reduce the mixer speed to low and slowly add the dry ingredients, scraping down the sides of the bowl as needed, until nearly combined. Add the chocolate chips and stir until just combined.

Roll the dough into 12 balls (about 65 g each). Cover them with plastic wrap and refrigerate or freeze overnight.

Preheat the oven to 400 F. Line two baking sheets with non-stick mats.

Place the cookies on the baking sheets and bake them for 13 minutes if chilled or 15 minutes if frozen. 

Let the cookies cool on the baking sheets for 10 minutes before transferring them to a wire rack to cool completely.