Creating Brownie Ice Cream Sandwiches can be easier if you follow these steps carefully:

1. Preheat Your Oven: Set your oven to 350°F (175°C) and grease a 9×13 inch baking pan.
2. Melt Butter: In a saucepan, melt the unsalted butter over low heat and remove it from the heat once melted.
3. Mix Sugar and Eggs: Stir in the granulated sugar until combined. Then, add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
4. Combine Dry Ingredients: In a separate bowl, sift together the flour, cocoa powder, salt, and baking powder.
5. Combine Mixtures: Gradually fold the dry ingredients into the wet mixture until just combined. Avoid overmixing.
6. Bake: Pour the brownie batter into the prepared baking pan. Smooth the top with a spatula and bake for about 25-30 minutes. The brownies should be set and a toothpick inserted in the center should come out with a few moist crumbs.
7. Cool: Once baked, remove the brownies from the oven and let them cool in the pan for about 30 minutes. Then, transfer them to a wire rack to cool completely.
8. Cut Brownies: Once completely cool, use a knife to cut the brownies into squares or rectangles, depending on your desired sandwich size.
9. Assemble Sandwiches: Place a scoop of ice cream on one brownie piece and top it with another brownie piece. Gently press them together to form a sandwich.
10. Optional Toppings: If desired, roll the edges of the sandwiches in chocolate chips, sprinkles, or nuts for an extra touch.