*If you do not have a 12 inch cast-iron skillet, you could bake these in a 10 1/2" x 7 1/2" baking dish. The bake time may vary by a few minutes, so watch it towards the end. I also tried baking this in a 13" x 9" baking dish, and I felt it turned out too thin and didn't bake through before getting too crispy at the edges. Just FYI.

In a bowl, stir together the flour, baking powder, and salt. Set aside.

In another bowl, cream together the butter and sugar. Stir in the eggs and vanilla. Now combine the flour mixture, the butter mixture, and melted chocolate in one bowl, and stir until just combined. Be sure to let the melted chocolate cool some before adding as super hot chocolate could begin to cook the raw eggs and make your batter lumpy (in a bad way).

Spoon the batter into a well-buttered cast-iron skillet. Top with peanut butter chips if using. Bake at 350°F for 32-35 minutes. If you like your brownie more gooey at the center, remove after 32 minutes. If you like it soft but baked through, then bake at the full 35 minutes. Test the center with a toothpick as oven temperatures and cook times can vary.