For the Muffins

1. Warm your oven to 400 degrees F. Line 20 muffin pan cups with paper liners.
2. In a medium bowl, whisk together the flour, cocoa powder, salt, baking powder, baking soda, and cinnamon. Keep this aside.
3. Cream the brown sugar and butter together until the mixture looks light and fluffy. Add the egg, vanilla, and sour cream. Beat until everything is well combined and smooth.
4. Gradually add the dry flour mixture and the milk to the butter mixture, alternating between adding a bit of dry and a bit of liquid ingredients.
5. Gently fold in the mini chocolate chips. Put the batter aside for now.

For the Cheesecake Layer

1. In a separate bowl, beat the softened cream cheese until it is smooth. Mix in the sugar until that is also smooth.
2. Add the egg and beat just until it is mixed in. Be careful not to over-mix the filling.

To Assemble

1. Spoon a small amount of the muffin batter into the bottom of each prepared muffin cup liner.
2. Add a layer of the cheesecake mixture on top of the batter.
3. Cover the cheesecake layer with the rest of the muffin batter.
4. Scatter the remaining mini chocolate chips over the top of each muffin.
5. Bake for 16 to 18 minutes. Check for doneness by inserting a toothpick into the center; it should come out with only a few moist crumbs attached.
6. Take the muffins out of the oven and let them cool in the pan for about 5 minutes. Then, transfer them to a wire rack to finish cooling completely.