Preheat the oven to 350°F (175°C) and line a muffin tin with cupcake liners.

In a mixing bowl, whisk together the flour, baking powder, cinnamon, and salt.

In another bowl, cream the softened butter and sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla.

Gradually add the dry ingredients to the wet ingredients, alternating with milk, and mix until just combined.

Spoon the batter into the prepared muffin tin, filling each liner about 2/3 full.

Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean.

Allow the cupcakes to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.

In a small bowl, mix together the granulated sugar and cinnamon for the topping.

Once the cupcakes are completely cool, brush the tops with melted butter and dip them into the cinnamon sugar mixture.

Drizzle the chocolate sauce over the top of each cupcake before serving.