Homemade chocolate chip cookie cake

Makes: 8 to 10 servings

For the cookie base:

Cooking spray

8 tablespoons (1 stick) unsalted butter

2⁄ 3 cup packed light brown sugar

1⁄3 cup granulated sugar

2 large eggs

1 1⁄2 teaspoons vanilla extract

2 cups all-purpose flour

1 teaspoon kosher salt

3⁄4 teaspoon baking soda

1 cup plus 2 tablespoons semisweet chocolate chips, divided

For the frosting and assembly:

4 tablespoons (1⁄2 stick) unsalted butter

2 tablespoons unsweetened cocoa powder

1 tablespoon plus 1 teaspoon milk

1⁄4 teaspoon vanilla extract

1 cup powdered sugar

2 tablespoons rainbow sprinkles

1. Make cookie base: Place 1 stick unsalted butter in the bowl of a stand mixer fitted with the paddle attachment for the cookie base (or in a large bowl if using an electric hand mixer) and 4 tablespoons unsalted butter for the frosting on the counter. Let sit out at room temperature until softened, about 45 minutes.

2. Arrange a rack in middle of oven and heat oven to 350 degrees. Coat 1 (9-inch) round cake pan with cooking spray, then line the bottom with parchment paper.

3. Add 2⁄3 cup packed light brown sugar and 1⁄3 cup granulated sugar to the bowl of butter. Beat on medium-high speed until light and fluffy, 2 to 3 minutes. Beat in 2 large eggs one at a time, waiting until the first one is fully incorporated before beating in the second. Add 1 1⁄2 teaspoons vanilla extract and beat just until combined, 1 minute.

4. Turn off mixer. Add 2 cups all-purpose flour, 1 teaspoon kosher salt and 3⁄4 teaspoon baking soda. Beat on low speed until incorporated, 1 to 2 minutes. Stir in 1 cup of chocolate chips by hand.

5. Transfer the dough to the baking pan and press into an even layer with your hands. (If the dough is too sticky, lightly coat your hands with cooking spray.) Sprinkle the remaining 2 tablespoons chocolate chips on top.

6. Bake until the top is lightly browned and no longer shiny, 20 to 25 minutes. Place the pan on a wire rack and let the cookie cool completely in the pan.

7. Make the frosting: Place the 4 tablespoons room temperature unsalted butter in the clean bowl of a stand mixer fitted with a whisk attachment. (Alternatively, use an electric hand mixer and large bowl.) Add 2 tablespoons unsweetened cocoa powder, 1 tablespoon plus 1 teaspoon milk and 1⁄4 teaspoon vanilla extract. Beat on low speed until smooth, 2 to 3 minutes. Turn the mixer off.

8. Add 1 cup powdered sugar and mix on low speed until combined, 1 to 2 minutes. Increase the speed to high and beat until the frosting is light, fluffy and doubled in volume, scraping down the sides of the bowl halfway through, 1 to 2 minutes total. Transfer the frosting into a piping bag fitted with a star tip or a zip-top bag and set aside.

9. Assemble the cookie cake: Place the cookie on a cake stand or serving plate. Pipe small, decorative mounds of the frosting around the edge of the cookie. Sprinkle the frosting mounds and cookie with 2 tablespoons rainbow sprinkles.