Preheat your oven to 350°F (175°C).
Grease a muffin tin with cooking spray or line it with muffin liners.
In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer on medium speed until light and fluffy, about 2-3 minutes.
Add in the large egg and 2 teaspoons of vanilla extract. Mix until well combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, mixing just until combined.
Gently fold in the funfetti sprinkles, being careful not to overmix.
Scoop the cookie dough into the prepared muffin tin, filling each cup about 2/3 full.
Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden.
Remove from the oven and allow to cool in the pan for about 5 minutes, then transfer to a wire rack to cool completely.
In a mixing bowl, beat the softened butter until creamy. Gradually add in the powdered sugar, mixing well. Add 1 teaspoon of vanilla extract and 1 tablespoon of heavy whipping cream. Beat until smooth and fluffy.
Once the cookie cups have cooled completely, frost each cup with the vanilla frosting.
For an extra festive touch, sprinkle additional funfetti on top of the frosting.
