Preheat oven to 350°F degrees. Line a standard muffin pan with 6 paper liners.

In a large bowl or stand mixer, cream together butter and sugar. Mix in egg and vanilla, beating until smooth. Scrape bowl as needed. Add spices, salt and baking soda. Mix in half of the flour, followed by the molasses. Mix in remaining flour and sour cream. Continue mixing until no streaks remain. 

Divide batter equally between prepared paper liners, using a large cookie scoop. 

Bake at 350°F for 20-22 minutes or until a cake tester or toothpick inserted comes out clean. Cool in pan until easy to handle, then transfer to a wire rack to cool completely. 

Meanwhile, prepare glaze. In a small bowl whisk together powdered sugar, vanilla and milk. Add additional powdered sugar or milk until desired consistency is reached. Drizzle glaze over cooled muffins. 

Store in an airtight container for up to several days.