Preheat oven to 350° F. Grease or paper line a standard-size muffin pan with 12 wells. Set aside.
Mix flour, baking soda, baking powder, and salt in a medium bowl.
Whisk buttermilk, sugar, egg, butter, and vanilla in a medium bowl until well combined. Add the peanut butter, whisking until well incorporated. Mix in dry ingredients with a spatula until just combined, making sure to scrape up from the bottom. Stir in half of the peanuts and 2/3 cups of chocolate chips.
Divide batter equally between muffin cups; they will be quite full. Sprinkle remaining chopped peanuts over the tops, pressing them in gently to adhere. Press several chocolate chips into the top of each muffin.
Bake until a skewer inserted in the middle of a muffin comes out mostly clean, about 15 to 20 minutes. Cool on a wire rack for at least five minutes before removing muffins from the pan.
Serve warm or at room temperature.