Preheat your oven to 350°F and line a 9x13 inch baking pan with parchment paper, leaving overhang on two sides. This overhang acts as handles for easy brownie removal later. Melt the butter in a microwave-safe bowl for 30-second intervals until completely liquid but not boiling hot.

Whisk together flour, cocoa powder, baking powder, and salt in a medium bowl until no cocoa clumps remain. I always sift my cocoa powder because lumps create uneven chocolate flavor throughout the brownies. Set this dry mixture aside while you work on the wet ingredients.

Beat the melted butter with both sugars in a large bowl until the mixture looks slightly grainy and lighter in color. Add eggs one at a time, beating well after each addition. Stir in vanilla powder, heavy cream, and whole milk until smooth and glossy.

Fold the dry ingredients into the wet mixture using a spatula, stirring just until no flour streaks remain visible. Overmixing develops gluten and creates tough brownies instead of tender ones. Fold in chocolate chips and pour batter into your prepared pan, spreading evenly to all corners.

Bake for 28-30 minutes until a toothpick inserted two inches from the edge comes out with just a few moist crumbs. The center should still look slightly underdone because brownies continue cooking as they cool. Let the pan cool completely on a wire rack for at least one hour before attempting to cut.

Remove the cooled brownie slab using the parchment overhang and place on a cutting board. Cut into 12 equal rectangles using a sharp knife, wiping the blade clean between cuts for neat edges. This is when your brownie ice cream sandwiches cozy really start taking shape.

Remove ice cream from the freezer and let it soften at room temperature for 5-7 minutes until scoopable but not melting. Place a generous scoop on the flat side of one brownie, then top with another brownie to create a sandwich. Gently press down until ice cream reaches the edges but doesn't squeeze out completely.

Wrap each assembled sandwich individually in plastic wrap and freeze on a flat baking sheet for at least 2 hours before serving. This firm freeze prevents the ice cream from oozing out when you bite through the brownie layers. The wrapped sandwiches store beautifully for up to two weeks in the freezer.