CHOCOHOLIC MUFFINS from Once Upon a Chef

This recipe is from Once Upon a Chef. It uses buttermilk (I made homemade w/vinegar), all brown sugar, and melted butter. I made half the recipe, filling the muffin cups 2/3 of the way, and got ten. They baked in 12-13 minutes on 375 degrees F. I didn't bake them at a real high temperature then turn it down like the recipe stated. They're very good and cake-like. They have a finer crumb than any chocolate muffin I've ever made before. I do think they need less cocoa powder, so I'll use less next time, not 1/3 c. like I used this time. I think for half the recipe I'll use only three tablespoons. They need more salt too though I did add extra. 

I grade these an A- because of too much cocoa.

Edit: I made half a batch again using all vegetable oil, no butter, an extra 1/8 t. salt and just 3 tablespoons of cocoa powder and they turned out great. Those I grade an A+.