Prepare the Cinnamon Swirl:
Mix melted butter, brown sugar, and ground cinnamon in a small bowl.
Make the Pancake Batter:
Whisk together flour, sugar, baking powder, and salt in a large bowl.
In a separate bowl, mix milk, vegetable oil, egg, and vanilla extract.
Combine wet and dry ingredients, stirring until just combined. Lumps are okay.
Cook the Pancakes:
Heat and grease a non-stick skillet or griddle over medium heat.
Pour 1/4 cup of batter onto the skillet for each pancake. Drizzle cinnamon swirl mixture on top and swirl with a toothpick.
Cook until bubbles form and edges look set, then flip and cook until golden brown.
Make the Glaze (Optional):
Whisk together powdered sugar, milk, and vanilla extract until smooth.
Serve and Enjoy:
Serve pancakes hot with glaze or desired toppings.