Step 1: Preheat your oven to 350°F (175°C) and lightly grease a donut pan. If you don't have a donut pan, a muffin tin can be used as an alternative.
Step 2: In a large bowl, whisk together the dry donut ingredients: flour, granulated sugar, baking powder, and salt. Ensure they are well combined.
Step 3: In a separate bowl, beat together the wet donut ingredients: eggs, whole milk, vanilla extract, and melted butter until fully combined.
Step 4: Pour the wet ingredients into the dry ingredients. Stir gently until just combined, being careful not to overmix. If using, fold in the mini chocolate chips at this stage.
Step 5: Spoon the donut batter into the prepared donut pan, filling each mold about halfway. This allows for proper rising.
Step 6: Bake for 10-12 minutes, or until a toothpick inserted into a donut comes out clean. Let them cool in the pan for a few minutes before transferring to a wire rack to cool completely.
Step 7: While the donuts cool, prepare the peanut butter filling. In a bowl, combine creamy peanut butter, powdered sugar, vanilla extract, and heavy cream. Mix until smooth and creamy. Add more heavy cream if needed for a spreadable consistency.
Step 8: Once the donuts are completely cooled, slice each donut in half horizontally to create two halves. Spread a generous layer of the peanut butter filling onto the bottom half of each donut.
Step 9: Sprinkle the chopped Reese’s Peanut Butter Cups evenly over the peanut butter filling on each donut half. Feel free to be generous with the topping!
Step 10: Carefully place the top half of each donut onto the filled bottom half, gently pressing down to form a sandwich. Serve immediately and enjoy!