Preheat the oven to 350°F and line two 9x9 baking dishes with parchment paper. Spray them with cooking spray, and set them aside.
Add the butter and chocolate chips to a medium-sized microwave-safe bowl. Microwave the butter and chocolate in 15-second intervals, stirring in between intervals until it's smooth.
Whisk in the sugar to the butter chocolate mixture until combined.
Then, whisk in the eggs one at a time, mixing in the first one fully before adding the next. Stir in the vanilla extract next.
Stir together the flour, cocoa powder, baking powder, and salt in a separate large bowl.
Add the wet mixture to the dry ingredients and stir them both together until it's all fully combined with no dry patches.
Add half of the batter to each prepared baking dish and bake them for 16-18 minutes, or until a toothpick inserted into the center comes out mostly clean. It is better to slightly undertake the brownies rather than overbake them, so if there are a couple of crumbs on the toothpick that is perfect.
Let the brownies cool completely in the pans before moving on.
Make sure the ice cream is softened but not completely melted. Carefully smooth the ice cream on top of one of the brownies while still in the pan.
Take the second brownie out and remove the parchment paper. Place it on top of the ice cream you just smoothed out and gently press it down.
Wrap the baking dish with foil and place in the freezer until frozen solid, about 6 hours.
When ready to serve, remove the foil and lift it out using the parchment paper to help. If they're sticking to the pan, run a butter knife along the sides of the pan and the parchment paper to help release it.
Take off the paper, and cut into 9 even bars, serve sandwiches immediately or pop them back into the freezer until you are ready to serve.