Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper and set aside.

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.

In a large bowl, using an electric mixer (stand mixer with paddle attachment or a hand-held mixer), cream together the softened unsalted butter, granulated sugar, and light brown sugar on medium speed until light and fluffy, about 2-3 minutes.

Beat in the large egg, vanilla extract, and almond extract (if using) until well combined and smooth, scraping down the sides of the bowl as needed.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.

Fold in the 1/2 cup of rainbow sprinkles with a rubber spatula until evenly distributed throughout the dough.

Chill the cookie dough in the refrigerator for at least 30 minutes. This helps prevent spreading and results in chewier cookies.

Once chilled, use a small cookie scoop (about 1.5 tablespoons) to drop rounded balls of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.

Bake one sheet at a time for 10-12 minutes, or until the edges are lightly golden and the centers are set but still look soft. Do not overbake. (Total cook time assumes two batches).

Remove from the oven and let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Cookies must be completely cool before frosting.

In a clean large bowl, using an electric mixer, beat the softened butter on medium speed until creamy, about 1-2 minutes.

Gradually add the sifted powdered sugar, 1 tablespoon of milk/cream, vanilla extract, and a pinch of salt. Start on low speed, then increase to medium-high once combined, beating for 2-3 minutes until light and fluffy. Add more milk/cream, 1 teaspoon at a time, until the desired consistency is reached.

Once the cookies are completely cool, spread a generous dollop of vanilla buttercream frosting on top of each cookie using a knife or offset spatula.

Immediately sprinkle additional rainbow sprinkles over the frosting before it sets. Serve and enjoy!