Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper. Whisk the flour, baking powder, baking soda and salt in a small bowl. Set aside.
In a larger bowl, whisk the sugar, vanilla, butter and eggs until smooth. Stir in the flour mixture in three batches to make a soft dough. Add your stir-ins and mix until combined.
Using a medium ice cream scoop (it should hold about 3 tablespoons of dough), scoop the dough onto the baking sheets, about 3 inches apart, and gently flatten the tops. Bake until the edges are just set, 11 to 13 minutes, rotating the pans halfway through the baking time. Cool on the trays for 5 minutes and then transfer to a wire rack to cool completely.
Cool the baking sheets and reline with new parchment. Bake the remaining cookies.
Once the cookies are cooled, scoop 1/2 cup of ice cream onto the bottom of half of the cookies and top each with another cookie. Eat.
Store any leftover cookies in a resealable plastic bag or container for up to 3 days.