In another bowl stir together flour, cornstarch, baking powder, and salt.
Incorporate the dry ingredients to the wet, mix until crumbly dough forms.
Separate dough equally into two bowls, add blue coloring to one bowl and red to the other.
Knead dough until dough is evenly colored, you may want to use food safe gloves to prevent dying hands.
Wrap each dough in plastic wrap and chill in the refrigerator for 3 hours or overnight.
Preheat the oven to 375°F.
Prepare 2 cookie pans by lining with parchment.
Roll out dough on a floured surface and cut out dough using a 2” circle cutter. Roll out to a little more than ⅛”. Reshape scraps into another ball and roll out one more time.
Bake cookies for 7 - 8 mins. Cool on a wire rack.
When cookies are totally cool, add one scoop of ice cream to a cookie and top with another color cookie. Wrap in plastic and immediately store in the freezer in a large airtight container. After making each sandwich, place in the freezer to avoid ice cream melting. Seal container when finished.
If rolling in sprinkles, let cookies freeze at least an hour before decorating. Then place it back in a wrapper and put it in the freezer.