Brown the Butter: In a light-colored pan, melt the butter over medium-high heat. Stir constantly for about 5 minutes until brown bits form at the bottom. Remove from heat and let cool for 40-45 minutes. This process deepens the flavor and gives the cookies a rich, toasty aroma.
Prepare for Baking: Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Mix Wet Ingredients: In a large mixing bowl, beat the cooled brown butter, granulated sugar, and brown sugar until light and fluffy. Add the egg and mix until fully incorporated. Then, add the yolk, vanilla extract, and cake batter extract, mixing until combined.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, salt, and baking soda to ensure even distribution of the leavening agent.
Mix Everything Together: Gradually mix the dry ingredients into the wet ingredients until just combined. Be careful not to overmix, as this can lead to tough cookies instead of the soft, chewy texture we’re aiming for.
Add Sprinkles: Gently fold in 4 tablespoons of rainbow sprinkles, making sure they are evenly distributed throughout the dough.
Form Cookie Dough Balls: Scoop 80g portions of dough and roll them into balls. Press the tops into additional sprinkles for a festive touch and extra crunch.
Chill the Dough: Place the dough balls on a baking sheet and refrigerate for at least 1 hour (or up to 72 hours for enhanced flavor). Chilling the dough helps prevent excessive spreading and intensifies the flavor.
Bake: Arrange 4 cookie dough balls on a prepared baking sheet, spacing them apart. Bake for 14 minutes until the edges are golden brown but the centers remain soft.
Cool & Enjoy: Allow cookies to cool completely on the baking sheet before enjoying their chewy, flavorful goodness! Letting them rest allows the flavors to fully develop and the texture to set.