Preheat oven to 350℉. Spray mini muffin tray with oil.
In a food processor, pulse together the dates and milk until mostly broken down and incorporated. Next, add in the peanut butter, cacao powder, baking soda, salt, egg, vanilla extract and pulse together until smooth and combined. The mixture will be very sticky, so I recommend using a mini cookie scooper. Transfer the batter to the mini muffin slots. You can top each bite with optional mini chocolate chips. Press them down gently with your finger tips. Bake for 12-14 minutes or until toothpick comes out mostly clean. Allow to set in the pan for 20 minutes then remove.