In a larger bowl, mix the butter and both sugars together until smooth. Mix in the egg and vanilla and stir until combined.
Stir in the flour mixture, followed by the dark chocolate chips.
Form cookie dough into 1” balls and drop onto greased cookie sheets. You should end up with about 2 dozen cookies.
Bake at 375 for 10-12 minutes. As soon as cookies come out of the oven, use the back of a large, flat spatula to smash them down flat (not required, but really flat cookies are so much easier to build into ice cream sandwiches, trust me).
Cool cookies completely. Once cool, take your ice cream out of the freezer and allow it to soften slightly.