You'll need:
2 1/4 cups all purpose flour
2 tsp baking powder
1/2 tsp kosher salt
6 tbs unsalted butter, melted and cooled
2/3 cup light brown sugar, packed
1/2 cup peanut butter (creamy, chunky, or both!)
2 extra large eggs
1/2 cup milk (2% or whole)
1/2 tsp vanilla extract
1/2 cup chocolate chips, heaping
1/2 cup peanut butter chips, heaping
Preheat the oven to 350 degrees F. Line a muffin tin with 12 paper liners.
Whisk together the flour, baking powder, and salt. In another bowl, whisk together the butter, brown sugar, peanut butter, eggs, and milk until smooth (mine was looking pretty soupy at this stage, so don't worry if yours does too).
Mix the wet and dry ingredients until just combined. Next, fold in the chocolate and peanut butter chips.
Fill the prepared muffin tins all the way to the top.
The Galley Gourmet's recipe says to bake them for 18-20 minutes, but I found that mine needed 22-23 minutes. At 18 minutes they were pretty raw on the inside. Bake them until a toothpick or a knife comes out clean. Cool them in the pan for ~5 minutes, then move them to a wire rack to finish cooling.
If you fill the paper liners up all the way to the top, you'll get 12, nicely domed muffins out of this recipe. And what can I say? It's chocolate + peanut butter + muffiny goodness. They are pretty awesome. They were great as a post-dinner snack, although I imagine that they would be good at any time of day.