Funfetti Cookie Cake with White Chocolate and Buttercream

Funfetti Cookie Cake

Funfetti cookie cake is one thick sugar cookie baked in a round pan, not a fluffy cake. Rainbow jimmies and white chocolate chips run through the soft, chewy center, while large vanilla-buttercream stars line the lightly golden edge. Cut it into wedges so each slice gets some frosting.

The dough comes together by hand with melted butter. For a soft center, take the cookie out when the top has lost its wet shine but still looks soft; it will firm as it cools. This recipe makes 8–10 wedges and takes about 1 hour 30 minutes, including cooling and decorating.

Ingredients for Funfetti Cookie Cake

For the cookie

• 1/2 cup unsalted butter, melted and cooled until warm (113g)
• 3/4 cup granulated sugar (150g)
• 1/4 cup packed light brown sugar (50g)
• 1 large egg
• 1 large egg yolk
• 1 teaspoon vanilla extract
• 1 1/2 cups all-purpose flour, spooned and leveled (190g)
• 2 teaspoons cornstarch (5g)
• 1/2 teaspoon baking powder
• 1/2 teaspoon fine salt
• 1/3 cup rainbow jimmies, plus 1 tablespoon for the top
• 1/2 cup white chocolate chips (85g), plus a few for the top

For the vanilla buttercream

• 1/2 cup unsalted butter, softened (113g)
• 2 cups powdered sugar (240g)
• 1 teaspoon vanilla extract
• 1–2 tablespoons heavy cream or half-and-half, as needed
• Pinch of fine salt

How to Bake Funfetti Cookie Cake

1. Prepare the pan: Preheat the oven to 350°F (175°C) with a rack in the center. Lightly grease the sides of a 9-inch round cake pan. Line the bottom with parchment and lightly grease the parchment.
2. Mix the wet ingredients: Whisk the melted butter with both sugars. Once the mixture is warm rather than hot, whisk in the egg, yolk, and vanilla until smooth.
3. Finish the dough: In a separate bowl, whisk the flour, cornstarch, baking powder, and salt. Fold into the butter mixture just until no dry flour remains, then fold in the jimmies and white chocolate chips.
4. Fill the pan: Press the dough into an even layer that reaches the edges without packing it down tightly. Scatter the extra jimmies and white chocolate chips over the top and press them in lightly.
5. Bake until just set: Bake uncovered, beginning to check at 20 minutes. Expect about 22–26 minutes in a 9-inch pan, though pan material and dough thickness can shift the timing. Remove the cookie when the edges are lightly golden and the center has lost its wet shine but still looks soft. Do not wait for the center to become firm.
6. Cool completely: Leave the cookie cake in the pan for about 45–60 minutes, until it no longer feels warm and is firm enough to handle. Carefully transfer it to a serving plate.
7. Make the buttercream: Beat the softened butter until smooth. Gradually beat in the powdered sugar, vanilla, and salt. Add the cream a teaspoon at a time until the frosting is smooth, holds a soft peak, and is thick enough to pipe.
8. Decorate and serve: Using a piping bag fitted with a large open-star tip, pipe large stars or rosettes around the cookie’s curved outer edge. Let the border set briefly, then cut into triangular wedges.

How to Keep the Cookie Cake Soft

Weigh the flour or spoon it into the measuring cup and level it off. Too much flour can make the cookie dry; mixing after the flour disappears can make it firmer. Use the lightly golden edge and no-longer-wet center to judge doneness, since the cookie continues to set in the pan.

Sprinkle and Frosting Tips

Use rainbow jimmies—the long sprinkles—in the dough. Small round nonpareils can bleed color or add an unwanted crunch.

Wait until the cookie is completely cool before transferring or frosting it. Warm cookie cake can break, and residual heat can melt the buttercream’s piped ridges. If the frosting is too stiff to pipe, add cream gradually; it should hold distinct stars along the edge.

Serving and Storing Funfetti Cookie Cake

Serve at room temperature so the cookie is soft. Vanilla ice cream is optional alongside a wedge.

Keep the frosted cake covered at room temperature for the day of serving, then refrigerate leftovers in an airtight container. Let chilled slices sit briefly at room temperature before serving. To make it ahead, bake and cool the cookie cake, then pipe the border on the day you serve it.

For longer storage, wrap the fully cooled, unfrosted cake tightly and freeze for up to 2 months for best quality. Thaw it, bring it to room temperature, and then decorate.

For another soft-centered cookie dessert, try Pecan Chocolate Chip Cookies. For a smaller filled-cookie dessert, see Cheesecake Cookies with Strawberry Jam Centers.

Nutrition

Approximate nutrition per 1/10 of the cookie cake: 500 calories, 4g protein, 23g fat, and 69g carbohydrates. Per 100g: about 465 calories, 3g protein, 21g fat, and 64g carbohydrates. Values vary with ingredients and portion size.