Preheat oven to 375°F. Grease a 13" x 9" metal baking pan with butter and line with parchment. Whisk flour, cocoa powder, milk powder, cinnamon, salt, and cayenne in a bowl.
Melt butter in a saucepan over medium heat. Remove from heat and add chocolate, granulated sugar, and brown sugar. Mix until glossy. Add eggs one at a time, then stir in vanilla. Fold in chocolate mixture into flour mixture.
Bake until a tester comes out with a few moist crumbs attached, 25 to 30 minutes. Let cool in pan before transferring to a wire rack.
For the frosting, beat confectioners’ sugar, butter, cocoa powder, cream, paprika, vanilla, and salt until smooth. Spread over brownies and sprinkle with paprika. Enjoy!