For the brownies: Preheat the oven to 375 degrees F and grease a 9-by-13-inch nonstick baking pan with cooking spray.
Melt the butter, chocolate, cinnamon, Aleppo pepper and chili powder together in the top of a double boiler or in the microwave (for 4 minutes). Stir with a rubber spatula until all the chocolate is melted. Remove from the heat and cool to room temperature.
Combine the eggs, granulated sugar, brown sugar and vanilla paste in a stand mixer fitted with the whisk attachment. Whip on high speed until the mixture becomes pale and pulls ribbons when the whisk is run through it, 2 to 3 minutes.
Fold the melted chocolate into the egg mixture with a rubber spatula, gently stirring from bottom to top until the chocolate is fully incorporated. Add the salt to the cake flour, then fold half of the flour into the egg and chocolate mixture until thoroughly combined. Fold in the remaining flour.
Pour the batter into the prepared baking pan making sure the batter is level and evenly spread in the pan. Bake until a cake tester comes out clean when placed in the center, 25 to 30 minutes. Let cool completely.
For the icing: Combine the cream cheese, butter, peanut butter, confectioners' sugar and salt in a large bowl with an electric mixer for 2 minutes. Wipe down the sides and the bottom of the bowl with a rubber spatula.
Spread the icing on top of the brownies in an even layer. Dust with cocoa powder, then cut and serve. Alternately, place the icing in a piping bag and pipe icing stars on top. Dust with cocoa powder, then cut and serve.