Preheat waffle maker
In a bowl of a stand mixer fitted with the paddle attachment, mix together 3 pounds brownie mix, 1.5oz malted milk powder, and 18oz buttermilk. Mix on low speed for two minutes, scrape the bowl, then 20 seconds on medium. Reserve.
In a bowl of a stand mixer fitted with the whip attachment, mix together 12oz egg whites and ¾ tsp cream of tartar. Whip to stiff peaks. Working in three batches, gently fold the whites into prepared batter. Using waffle maker according to manufacturer’s directions, pour batter into sprayed waffle maker and cook until the outside is crispy.