Beat 1 cup softened butter and 1 1/4 cups granulated sugar on medium-high for 3 to 4 minutes until pale and fluffy. Add 2 eggs one at a time, then mix in 2 tsp vanilla extract and 1 tsp almond extract.

Whisk together 2 3/4 cups flour, 1/2 tsp baking powder, 1/2 tsp baking soda, and 1/2 tsp salt in a separate bowl. Add to the butter mixture in 2 additions on low speed, mixing just until combined. Fold in 3 tbsp jimmies by hand.

Preheat oven to 375°F (190°C) and line 2 baking sheets with parchment. Scoop 3 tbsp of dough per cookie, place 3 inches apart, and press each ball down slightly. Bake 11 to 13 minutes until edges are set and centers look just underdone. Cool on the pan for 10 minutes, then transfer to a wire rack.

Beat 1/2 cup softened butter for 1 minute. Add 2 cups sifted powdered sugar, 1 tsp vanilla extract, and 1/2 tsp almond extract. Mix in 2 tbsp heavy cream and beat on medium-high for 2 minutes until smooth.

Spread frosting onto fully cooled cookies and top each with a pinch of rainbow sprinkles.