In a large bowl, whisk together flour, baking powder, brown sugar, salt, and cinnamon.
In a separate bowl, whisk together milk and sour cream, then add eggs one at a time. Stir in vanilla.
Add wet ingredients to dry ingredients and stir with a wooden spoon until just combined.
Melt butter in a large nonstick skillet over medium heat. When the butter is foamy, reduce heat to medium-low and ladle pancake batter into skillet. Cook until bubbles start to form in batter and the pancake is golden underneath, about 3 minutes. Flip and cook the other side until golden, another 3 minutes.
Immediately toss pancakes in cinnamon-sugar.
Repeat with remaining batter. Serve immediately with melted chocolate.
Notes
Serve with additional cinnamon-sugar for extra sweetness.