3/4 cup (105 g) basic gum free gluten free flour blend (69 grams superfine white rice flour + 23 grams potato starch + 13 grams tapioca starch/flour)
3/4 cup (60 g) Dutch-processed cocoa powder (if you use natural cocoa powder instead, add 1/8 teaspoon baking soda to the recipe)
1/4 teaspoon kosher salt
1/3 cup (67 g) granulated sugar
3/4 cup (164 g) packed light brown sugar
2 eggs (100 g, weighed out of shell) at room temperature, beaten
1 tablespoon pure vanilla extract
9 tablespoons (126 g) unsalted butter, melted
3 ounces bittersweet or unsweetened chocolate, melted
2 tablespoons (1 fluid ounce) heavy cream, at room temperature
2 quarts softened or homemade vanilla ice cream
Preheat your oven to 350°F. Grease two 8-inch x 8-inch baking pans lightly then line them with parchment paper that overhangs all 4 sides of the pan, or line with nonstick aluminum foil. Set the pans aside.
In a large bowl, place the flour blend, cocoa powder, salt, and granulated sugar, and whisk to combine well. Add the brown sugar, and whisk again to combine, breaking up any lumps. Add the eggs and vanilla, then the melted butter, and melted chocolate, and the cream, and mix to combine. The batter should be thick but smooth. Divide the batter equally among the two prepared baking pans (each pan will have about 400 grams of batter), and spread into an even layer in each with a wet spatula.
Place the pans in the center of the preheated oven and bake just until firm to the touch (about 20 minutes). Allow the brownies to cool completely in the pans. Transfer one cooled brownie layer from the baking pan to a flat surface like a small cutting board or baking sheet, and place in the freezer for about 20 minutes. Chilling that layer will make it easier to transfer it to the top of the ice cream without its breaking.
Pour one recipe of homemade ice cream or softened store-bought vanilla ice cream over the top of the brownies still in their pan. Spread into an even layer. Top with the other brownie layer, top facing up. Freeze completely, still in the pan. Remove from the freezer, slice into rectangles and serve. Wrap any leftover ice cream sandwiches tightly and freeze for up to 2 weeks.