Preheat the oven to 375°F (190°C). Line a 12-count muffin pan with liners and set aside.
In a large mixing bowl, whisk together the flour, baking powder, ground cinnamon, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using a handheld mixer, cream the butter, brown sugar, and granulated sugar together for 3-4 minutes or until light and fluffy.
Mix in the eggs one at a time, then mix in the vanilla extract and sour cream, stopping to scrape down the sides of the bowl as needed.
Mix in the dry ingredients in two additions alternating with the milk, making sure to mix in each addition until just combined. Gently fold in the chocolate chips.
Evenly distribute the batter between all 12 muffin liners, filling each one to the top. Sprinkle each one with additional chocolate chips if desired. Bake at 375°F (190°C) for 18-23 minutes or until a toothpick inserted into the center of the muffins comes out clean.
Remove from the oven and allow to cool in the pan for 5 minutes, then carefully remove the muffins from the pan, and transfer to a wire rack to cool completely.