chocolate. whisk in the eggs one at a time, mixing each until smooth. stir the baking powder into the flour, then stir the mixture into the batter with a spatula just until no white streaks remain.
cut the cooled brownie layer in half the short way, wrap the layers in plastic, and freeze until the ice cream is ready, or at least 1 hour.
line the same pan you used to bake the brownie with plastic wrap, extending it well beyond the edges on all four sides. place one brownie layer top-side down in the pan and spread ice cream over it in an even layer. top with the second brownie layer, 