Blueberry Streusel Muffins

This is the first recipe I have ever made that has the ingredient sour cream. This is a big step for me. It doesn't use much, so I just decided to suck it up and try it. I couldn't tell so I might be willing to try other recipe containing sour cream.

2 1/4 cup all-purpose flour, divided
1/2 tsp baking soda
1 tsp baking powder
1/2 tsp table salt
1 large egg(s)
1 cup sugar, divided
3/4 cup reduced-fat sour cream
1 tsp vanilla extract
1/4 cup fat-free skim milk, divided
2 cup blueberries, washed and picked over
2 Tbsp butter, melted

Preheat oven to 375ºF. Place muffin liners in a 12-hole muffin tin.

In a large bowl, combine 2 cups of flour, baking soda, baking powder and salt; set aside.

Using an electric mixer, beat egg with 3/4 cup of sugar in a large bowl until light and fluffy. Add sour cream and beat until thoroughly combined; blend in vanilla extract.

Add half of flour mixture and half of milk to sugar mixture; beat until just combined. Add remaining flour mixture and milk; beat until smooth.

Fold in blueberries and fill each muffin liner about 3/4 full; set aside.

To make streusel topping, in a small bowl, combine remaining 1/4 cup each of sugar and flour. Pour in melted butter and combine with fingertips. Divide crumb mixture over muffins; gently press into top of muffin batter with fingertips.

Bake until slightly golden and a toothpick inserted in center of a muffin comes out clean, about 30 to 35 minutes. Cool in pans for about 10 to 15 minutes and then transfer muffins onto racks to cool completely.