Preheat oven to 350 degrees.
Prepare an 8x8 or 9x9 pan, covering pan with aluminum foil, then lightly grease foil.
Melt butter in saucepan on lowest setting until melted.
Add chocolate chips to melted butter, whisking until melted.
In a large mixing bowl, use a large whisk, lightly beat the eggs.
Place the sugars and salt in a small mixing bowl, add eggs and whisk until just incorporated.
Whisk the melted chocolate, then add into egg mixture and whisk until combined. Whisk in vanilla.
Whisk together the flour, baking powder, and cocoa powder together in a small bowl.
Sift dry ingredients over batter and stir in with silicone spatula until just combined.
Fold in chopped Whoppers and pour into pan, spreading out with spatula.
Bake for 25 - 35 minutes depending on size pan. Check center doneness by inserting a toothpick until it comes out clean.
Transfer pan to cooling and rack and let cool. Place in fridge to speed up process, 15 minutes after taking out of oven. (Brownies and cakes are easiest to frost when refrigerated and are cold.)