Preheat the oven to 400°F. Spray a mini-muffin pan with nonstick cooking spray, or place mini muffin paper liners in the cups and spray with non-stick cooking spray.
In a small bowl, combine the milk and vinegar; set aside.
In a medium mixing bowl, whisk together the flour, baking powder, sugar, and salt.
Slowly whisk in the milk mixture to the dry mixture, whisking just until incorporated.
Next, whisk in the slightly beaten eggs, vanilla extract, and the melted and cooled butter. Stir until all ingredients are well combined.
Fill the prepared mini muffin cups ⅔ full with the pancake batter. Add toppings of your choice to the top, if desired.
Bake the pancake muffins at 400°F for 15 minutes, or until lightly golden brown on top.
Serve warm with pancake syrup.