Cream butter and sugars in a mixing bowl. Beat in egg and vanilla. Whisk together flour, cocoa, baking powder, soda, and salt; stir into creamed mixture till well combined.
Scoop into tablespoon sized portions, then roll into balls. Place on lightly greased or silpat lined cookie sheets. Flatten with a glass dipped in sugar. Sprinkle with chocolate chips. Bake at 375° for about 8 minutes. Cool completely on wire racks.
To assemble, place a scoop of ice cream (about 1/4 cup) on the bottom of a cookie. Top with another cookie and press together. Serve immediately or wrap in plastic wrap and freeze.