In a large bowl, whisk together 1 and ¾ cups all-purpose flour, 1 teaspoon baking soda, ½ teaspoon baking powder, and ⅛ teaspoon salt; set aside.

In a separate large mixing bowl, beat ½ cup unsalted butter (softened) with 1 cup granulated sugar until light and fluffy, about 2 minutes.

Add 1 large egg and 2 teaspoons vanilla extract to the butter-sugar mixture and beat until combined.

Add the dry ingredients to the wet ingredients all at once and mix briefly—just until the flour is incorporated (about 5 seconds). Do not overmix; scrape the bowl as needed.

Fold in ½ cup funfetti until evenly distributed.

Cover the dough and chill in the refrigerator for at least 2 hours (or overnight) until firm.

When ready to bake, preheat the oven to 375°F and spray a mini muffin pan with baking spray.

Use a small cookie scoop to portion the chilled dough directly into the mini muffin cups, filling each cup nearly to the top (the dough will spread).

Bake for 8 to 10 minutes, until the edges are set and centers are still slightly soft (about 9 minutes is typical).

Remove the pan from the oven and let the cookies cool in the pan for 5 minutes. While still warm and pliable, gently press the center of each cookie with the back of a small spoon (or similar tool) to form a cup shape.

Transfer the cookie cups to a wire rack and cool completely.

For the frosting, beat ½ cup unsalted butter (softened to room temperature) in a large bowl until creamy.

Add powdered sugar (3 to 3.5 cups), one cup at a time, mixing well after each addition and scraping the bowl as needed, until the frosting reaches your desired thickness.

Add 1 teaspoon vanilla extract and 1 Tablespoon heavy whipping cream; beat the frosting for 2 minutes until smooth and spreadable.

Fill a piping bag with the frosting and pipe into the cooled cookie cups.