Preheat oven to 350°F and grease a mini muffin pan.
In a bowl, whisk together the milk, egg, melted butter or oil, and lemon zest.
Stir in the pancake mix until just combined.
Fold in the frozen blueberries. No need to thaw them first.
Fill the mini muffin cups to the top.
Bake for 15 minutes, or until cooked through.