Heat oven to 350°F (175°C). Prepare a second cookie sheet by lining it with parchment paper or a silicone baking mat.

In a stand mixer bowl equipped with the paddle attachment (or a large bowl using a hand mixer), combine the softened butter, granulated sugar, and brown sugar on low speed until light and fluffy. Add the egg and cake batter extract, mixing on medium speed until fully incorporated.

Stir in the baking powder and salt, then add the flour in increments, mixing just until the dough is smooth and cohesive, scraping down the bowl as necessary. Gently fold in the sprinkles.

Prepare a cookie sheet by lining it with a silicone baking mat or parchment paper. Drop 2- or 3-tablespoon portions of dough onto the sheet, leaving 3–4 inches between them depending on size. Use the bottom of a drinking glass to lightly press each portion flat.

Bake for 13–16 minutes for 2-tablespoon cookies or 18–20 minutes for 3-tablespoon cookies, until the edges are lightly golden and the centers are no longer shiny. Allow to cool completely before adding frosting.

For the frosting: In a very large bowl, beat the butter with a stand or hand mixer until smooth. Gradually incorporate the powdered sugar until the mixture becomes crumbly, then add the salt and extract. Pour in 2 tablespoons heavy cream and beat until smooth and fluffy, adding additional cream as needed to achieve the desired consistency.

Spread frosting over the cooled cookies as desired and garnish with additional sprinkles. To frost in the style of Crumbl, transfer frosting to a pastry bag fitted with a round tip and pipe in a spiral pattern.

Keep cookies in an airtight container for up to 3 days. For longer storage, freeze for up to 3 months.