Preheat oven to 350°F (175°C). Line a 9×13 inch baking pan with parchment paper, leaving overhang on both sides for easy lifting.

1. In a bowl, whisk together melted butter and sugar. Add eggs and vanilla, and mix until smooth.
2. Sift in cocoa powder, flour, salt, and baking powder. Stir until fully combined and smooth.
3. Spread batter evenly into prepared pan. Bake for 18–22 minutes or until a toothpick inserted comes out with a few moist crumbs.
4. Let brownies cool completely in the pan. Then lift them out using parchment and cut in half crosswise (to make two large rectangles).
5. Soften ice cream slightly at room temperature, then spread evenly over one half of the brownie slab.
6. Place the second brownie slab on top. Press gently and wrap tightly in plastic wrap. Freeze for at least 2 hours or until firm.
7. Once firm, slice into individual sandwiches. Serve immediately or store in the freezer until ready to enjoy.