Step 1

Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. Set aside.

Step 2

In a large bowl, whisk the flour, baking powder, baking soda, cinnamon, and salt together. Set aside.

Step 3

In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter on high speed until smooth and creamy, about 1 minute. Add the brown sugar and beat on high until creamed, about 2 full minutes. Scrape down the sides and bottom of the bowl as needed. Add the eggs, sour cream, and vanilla extract. Beat on medium speed for 1 minute, then turn up to high speed until the mixture is combined. Scrape down the sides and bottom of the bowl as needed.

Step 4

Pour the dry ingredients into the wet ingredients and beat on low speed until just about combined. Add the milk and continue to beat on low until combined. Fold in add-ins. (See flavors/details in the notes below.)

Step 5

Spoon the batter evenly into each cup or liner, filling each all the way to the top. Bake the muffins for 5 minutes at 425 then, keeping the muffins in the oven, reduce the oven temperature to 350°F (177°C). Bake for an additional 15-18 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 22-23 minutes, give or take. Allow the muffins to cool for 5 minutes in the muffin pan, then transfer to a wire rack to continue cooling.

Step 6

Glazed muffins stay fresh stored in the refrigerator for 1 week, unglazed muffins stay fresh stored at room temperature for a few days—then transfer to the fridge for up to 1 week.