Brownie recipe:
 2 eggs
1/2c. plus 2T. unsweetened cocoa powder
1/2 teaspoon salt
1/2 teaspoon baking powder
1/2 Tablespoon vanilla extract

 
1/2 cup butter
1c. plus 2T. sugar
3/4 cups all purpose flour

Directions:

Preheat oven to 350 and line 8×8″ pan with nonstick foil.
In a large bowl, add eggs, and beat with cocoa, salt, baking
powder, and vanilla. Stir until fully combined and
smooth.
In the microwave, melt butter. When melted, add sugar, and stir to
combine.
Add warm butter/sugar mixture to the egg/cocoa mixture, stiring until
smooth.
Add the flour to batter and stir until fully incorporated.
Spread batter into prepared pan, and smooth as needed.
Bake brownies about 25-30 minutes. Test for doneness by inserting a
toothpick.  You should find moist crumbs. Cool and chill 2 hours.

Top with Buttercream:
Electric Mix:

1/4 cup butter, softened to room temperature
1 and 3/4 cups confectioners’ sugar
3 Tablespoons heavy cream
Fold in:
6 Oreos, crushed
Spread onto brownies and chill 10 minutes.


Pour on the Chocolate Ganache

4 ounces semi-sweet chocolate*
1/2 cup heavy cream 
2 Tablespoons butter, softened to room temperature
Heat cream and pour over the chocolate stirring to melt chips.  Whisk in butter.

Chill bars and cut once cold.  Add white chocolate drizzle and chopped oreos, if desired!
frosting and ganache adapted from Sally’s baking addiction
  Adapted from King Arthur Flour