01 - Preheat oven to 350°F. Grease a 24-cup mini muffin tin thoroughly.
02 - In a large bowl, cream together butter, brown sugar, and granulated sugar until light and fluffy.
03 - Beat in eggs one at a time, then mix in vanilla extract.
04 - In a separate bowl, whisk flour, baking soda, and salt. Gradually add dry ingredients to the wet ingredients, mixing until just combined.
05 - Fold semisweet chocolate chips into the dough.
06 - Scoop about 1 tablespoon of dough into each muffin cup, pressing slightly to form a cup shape.
07 - Bake for 10-12 minutes, until lightly golden.
08 - Remove from oven and immediately use the back of a spoon to gently press down the centers to form a deeper cup shape.
09 - Cool the cookie cups in the pan for 10 minutes, then transfer to a wire rack to cool completely.
10 - Beat butter until smooth. Gradually add powdered sugar, alternating with milk, until fluffy. Mix in vanilla.
11 - Divide frosting into three portions. Leave one plain, tint one with red food coloring, and one with blue food coloring.
12 - Pipe or spoon frosting into cooled cookie cups. Decorate with red, white, and blue sprinkles.