Preheat the oven to 350°F (180°C). Spray a mini muffin tin liberally with non-stick spray, set aside.
Cream together the butter and granulated sugar until well combined. Then add in the egg.
1/3 cup (73g) salted butter, room temp, 1/2 cup + 1 Tbsp (117g) granulated sugar, 1 large egg
Once combined, add in the sour cream and vanilla.
1/4 cup (60g) sour cream, 1 1/2 tsp vanilla extract
Next, add the flour, baking powder, and salt and mix on low speed. As the dry ingredients begin to incorporate, slowly add the milk. Mix until a thick batter forms.
3/4 cup (heaping) (114g) all-purpose flour, 1/2 tsp baking powder, 1/8 tsp salt, 2 1/2 Tbsp milk
Divide the batter into the prepared mini muffin tin, approximately 1 Tbsp of batter for each muffin.
Bake at 350°F (180°C) for 15-17 minutes or until a toothpick comes out with a few moist crumbs on them.
Let the muffins cool for 10-15 minutes.
While the muffins are cooling, melt the butter for the snickerdoodle topping and stir the sugar and cinnamon together.
1/2 cup (111g) butter, melted, 3/4 cup (173g) granulated sugar, 1 Tbsp cinnamon
When the muffins are cool enough to handle, remove a muffin and roll in the melted butter and then in the cinnamon and sugar mixture to coat. Repeat with remaining muffins.
Enjoy! Store at room temperature in an airtight container or bag for up to 4 days or freeze for up to 3 months.