Preheat the oven to 375F (190C) degrees. Line a regular-sized muffin pan with muffin papers (you'll end up with 12-14 muffins total).
In a large bowl whisk together the flour, baking powder and salt. Set aside.
In a separate large bowl whisk together the oil, brown sugar and peanut butter. I recommend warming up the peanut butter for 30 seconds on medium power in the microwave first.
Whisk the eggs, vanilla and buttermilk into the oil mixture until smooth.
Make a well in the middle of the dry ingredients and pour the wet ingredients into the bowl. Gently fold the mixture together. If there are lots of lumps of flour, whisk by hand using a wire whisk to remove the lumps.
Gently fold in about ¾ cup chocolate chips (save the remaining ¼ cup for later).
Spoon the batter into the prepared muffin pan, filling each about ¾ full (you'll end up with 12-14 muffins total). Add a few extra chocolate chips to the top of each unbaked muffin.
Bake for 16-18 minutes in the middle of the preheated oven, or until an inserted toothpick comes out clean (except for the melted chocolate chips).
Cool muffins in the pan for about 10 minutes, then carefully transfer to a wire rack to continue cooling.
