In large mixing bowl, cream 3/4 cup unsalted butter, softened, 1/2 cup granulated sugar and 2/3 cup packed brown sugar until light, about 2 minutes.
Add in 3 large eggs, beaten, followed by 1 1/2 tsp vanilla extract
Mix in 3/4 cup chocolate malted milk powder.
Sift or whisk 1 3/4 cup all-purpose flour, 1 tsp baking powder and 1/4 tsp saltadd to batter in separate batches.
Pour into a greased 9"x13" baking pan and bake at 350°F for 20-25 minutes or until a toothpick inserted into the center of the pan comes out clean.
Cool completely before frosting.
For the frosting
Cream4 Tablespoons unsalted butter until light. Add in 2 1/2 cups powdered sugar and 1/4 cup chocolate malted milk powder. Slowly mix in 2-3 tbsp heavy cream or half and half until of spreading consistency. Spread on cooled brownies and cut into squares.
Notes
Cool brownies completely before frosting
Store frosted brownies in an airtight container for up to 72 hours
Brownies may be frozen in an airtight container for up to 45 days