Perfect cinnamon roll pancakes!
In a medium bowl, stir together the butter, brown sugar, and cinnamon and place into a pastry bag or plastic baggie. Set aside.
In a medium bowl, whisk together the flour, baking powder, and salt. Whisk in the milk, egg, vanilla extract, and oil, until incorporated.
Using a 1/8-1/4 size measuring cup, pour batter onto skillet. Spread the batter out more if necessary, to about 4-inch diameters.
When your pancake begins to form bubbles around the edges, pipe the filling. Starting at the center of the pancake, squeeze the filling on top of the pancake batter in a swirl, just as you see in a regular cinnamon roll.
Cook the pancake 2 to 3 minutes, or until the bubbles begin popping on top of the pancake and it's golden brown on the bottom.
Gently but quickly flip over pancake. Cook an additional 2 to 3 minutes (with temperature still on medium low), until the other side is golden as well.