Preheat oven to 350°F. Line a 24-cup mini muffin pan with liners and spray with non-stick cooking spray.
In a large bowl, whisk together the flour, sugar, baking powder and salt.
In a medium bowl, whisk together the milk, eggs, peanut butter, and yogurt until smooth. Add the wet ingredients to the dry ingredients and stir until well combined.
Divide half of the batter evenly amongst the prepared muffin cup liners, filling each muffin cup about halfway full. Top the batter in each muffin cup with about 1/2 teaspoon of jelly and then divide the remaining batter evenly amongst the tops of the jelly in each muffin cup, filling each muffin cup heaping full. Using a toothpick, barely swirl 1/2 teaspoon of jelly into the top of the batter of each muffin.
Bake for about 20 minutes or until the muffins have risen and a toothpick inserted in the center comes out batter-free. Let cool in pan 10 minutes before transferring to a wire rack to cool completely. Store in an airtight container.