Melt butter in a large saucepan over medium heat. Stir occasionally. The butter will foam up, then back down and start forming brown colored milk solids or “bits”. When it is light brown and starts to smell like you could drink it straight, that’s when you know it’s done. (Here’s a good lesson on browned butter.)
Meanwhile in a stand mixer or large bowl combine the sugar, cocoa powder, and salt. Add the butter when it is nice and brown, and beat it together.
Add the water and vanilla and beat again.
Add the eggs, one at a time, beating thoroughly between each addition.
Add the flour and stir until it is just barely incorporated.
Line a 9x13 inch pan with parchment paper. Or line it with foil and spray with nonstick spray, or you can spray the pan itself.
Spread the batter into the pan. Bake for 25-30 minutes, or until the toothpick inserted comes out clean.
Let cool completely.
Cut the brownies into small squares, or use a 2-inch biscuit cutter to make circles. Dip a knife in very hot water, then wipe dry with a cloth. Then slice each brownie horizontally, so that you can fill it like a sandwich.
Make the frosting: Cream the butter with a mixer until smooth. Add one cup of powdered sugar and combine. Add 1 tablespoon of cream, then another cup of powdered sugar. Add the vanilla. Add in the rest of the cream and powdered sugar in increments.
Spread a tablespoon or two of the frosting on the cut side of a brownie and cover with the top half. Then smoosh it in your face!
Notes
This recipe is really easy to cut in half. Bake the brownies in an 8x8 inch pan.Source: Oreo idea from The Food Charlatan, brownie recipe adapted from here.