Combine melted butter, eggs, milk, and baking powder in large mixing bowl.
Add in chocolate cake mix, stir until blended.
Stir in chocolate chunks, just until mixed.
Fill liners ¾ way full or fuller for less muffins but higher muffin top (will get less muffins this way).
Bake for about 20 minutes. Check muffin with toothpick. They are done with muffins come out clean - do not over bake. They will become dry.
Remove from muffin tins to remove from heat.
Video
Notes
Tip: To achieve a fuller muffin fill liners all the way. Tip: Resist the temptation to open the oven while the muffins are rising. It will cause the muffins to fall.