Preheat the oven to 350 F. Prepare 13" x 9" pan with parchment paper.
In the pan melt butter, add sugars, cocoa powder and chocolate chips. Melt everything on low heat. Remove from the heat, cool off a little. Add eggs and vanilla extract. Mix until all ingredients are well combined. Fold in flour. Pour the batter into the pan.
Bake for about 25 minutes. Remove from the oven and cool off completely.
Mousse
Mix 2 Tbsp. hot water with cocoa powder. Cool off completely.
Mix cream cheese, add water with cocoa. Add milk and chocolate jell-o.
Fold in cool whip or truwhip.*
Spread nicely on the brownies.
Extras
Decorate with crushed peppermint candy canes.
Notes
*I find it hard to mix the mousse, so I mix cool whip (truwhip) with all ingredients, it is easier that way to combine all ingredients together.