In a bowl, whisk together flour, sugar, baking powder, and salt.
Add milk, egg, melted butter, and vanilla extract and mix until smooth.
In a separate bowl, mix brown sugar, cinnamon, and softened butter to make the filling.
Transfer the cinnamon filling into a piping bag or zip bag.
Heat a non-stick pan over medium heat and lightly grease it.
Pour pancake batter onto the pan to form circles.
Pipe a spiral of cinnamon filling on top of each pancake.
Cook until bubbles form, then flip carefully and cook the other side.
Mix powdered sugar and milk to prepare the glaze.
Drizzle glaze over warm pancakes and serve immediately.