Preheat oven to 350 degrees. Grease a 9-inch square baking pan.
Melt butter and cocoa together in a bowl in the microwave, stirring every 30 seconds, until smooth. Stir in sugar, espresso powder, and vanilla.
Add eggs one at a time, mixing until combined. Add flour, baking powder, and salt; mix until well combined. Spread batter into prepared pan and bake 20-25 minutes or just until brownies start to pull away from the sides of the pan.
Sprinkle marshmallows, almonds, and chocolate chips on brownies. Heat broiler and place rack 8 inches from element. Broil brownies until marshmallows turn golden brown, about 2 minutes. Remove from oven, let cool 20 minutes, then refrigerate.
To cut, loosen brownies from the sides of the pan using a bench knife coated with non-stick spray.