I just made this up today. It worked brilliantly well. No cupcake liners, no cupcake pan, just mix and dump and go.
Muffin Mix Coffee Cake
2 small (6 muffins each) OR 1 large (12 muffins) muffin mixes of your choice
whatever the mixes call for
Preheat oven to 400.
Pour both muffin mixes into a bowl. Mix as directed, just until moistened. (I usually use the cheap mixes that come in bags and make 6 muffins each, but this works with the 12-muffin mixes that come in a box too.) Batter will probably be lumpy.
Pour batter into a greased 8x8 glass or metal baking pan. Bake for 15-20 minutes, until golden brown on top and toothpick comes out clean.
Allow to cool a few minutes before cutting into squares. (I did 16 squares, but 9 would be fine too if you have bigger appetites.) Eat.
If you have a muffin mix with a streusel topping, just sprinkle that on top before baking! If you want to make your own streusel topping, here's a quick recipe:
Streusel
1/4 cup brown sugar -- firmly packed
1/4 cup white sugar
1/4 cup flour
1 tsp cinnamon (optional)
2 Tbsp cold butter -- cut into chunks
Mix everything except butter in a small bowl. Add butter and cut it into the dry mix using a pastry blender, pastry knife, or two knives until it has become a coarse and meal, like tiny gravel. Sprinkle over coffee cake batter before baking.