Stacked mini brownie cakes can replace a wedding cake or be part of the dessert buffet. Decorate these with royal icing, sanding sugar, grated coconut, or confectioners' sugar.
Preheat oven to 350 degrees. Coat two 9-by-13-inch baking pans with cooking spray. Line bottoms with parchment paper, and coat with cooking spray. Dust with flour, tapping out excess. Set aside.
Melt chocolate and butter in a heatproof bowl set over a pan of simmering water, stirring until smooth. Set aside.
Put granulated sugar and eggs in the bowl of an electric mixer fitted with the whisk attachment; mix on medium-low speed until pale and fluffy, scraping down sides as needed, 2 to 3 minutes. Reduce speed to low. Add chocolate mixture; mix until combined. Mix in vanilla, flour, and salt.
Divide batter between the prepared pans. Bake, rotating halfway through, until a cake tester inserted in the centers comes out mostly clean, about 25 minutes. Transfer to wire rack to cool completely.
Invert brownies onto a work surface; remove parchment. Cut out five 2 1/2-, 1 3/4-, and 1 1/4-inch circles from each. Turn each circle right side up. Stack largest on bottom to smallest on top. Just before serving, sprinkle with confectioners' sugar.