Preheat oven to 350 degrees and line muffin tins with 15 liners.

In a large bowl, whisk together the bananas, eggs, oil, milk and vanilla.

In a separate large bowl, whisk together the flour, sugar, Jif Peanut Powder, salt and baking soda.

Add the flour mixture to the banana mixture and stir with a spatula until combined.

In a clean bowl, mix together one cup of the muffin batter with the melted bittersweet chocolate.

Add the chocolate batter back to the banana batter and mix gently until lightly swirled.

Fill the 15 muffin liners with about 1/4 cup of batter each.

Bake for 13 - 15 minutes, or until the tops of the muffins spring back when lightly touched.

Allow muffins to cool completely and store in an air-tight container on the counter for up to 3 days.