Preheat an oven to 350 degrees F (175 degrees C). Line 48 muffin cups with paper liners.
Whisk together the brownie mix, 2 eggs, 1/2 cup canola oil, and 1/4 cup water in a bowl. Stir just until fully incorporated, about 50 strokes; set aside.
Mix the cake mix, 2 tablespoons canola oil, 1 1/3 cup water, and 3 egg whites in a large bowl with an electric mixer on low speed until combined. Mix on medium speed for 2 minutes.
Spoon the brownie batter into prepared muffin cups, filling each cup 1/3 full. Spoon the cake batter over the brownie batter, until muffin cups are each 2/3 full.
Bake in the preheated oven until golden and the tops spring back when lightly pressed, about 20 minutes.
