Preheat oven to 375. Place muffin liners in muffin tins. (15)
Combine 2 c flour, baking soda, baking powder and salt; set aside.
Mix sugar and Splenda; set aside.
Using an electric mixer, beat egg with 3/4 c sugar/Splenda mix until light and fluffy. Add sour cream and beat until thoroughly combined; blend in vanilla.
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, do not over-beat.
Fold in blueberries and fill each muffin liner; set asided.
To make streusel topping, combine remaining sugar/Splenda mix and 1/4 C flour. Melt Smart Balance and add. Mix with a fork. Divide crumb mixture over muffins and press into top of muffin batter if necessary.
Bake until slightly golden and a toothpick inserted in center of a muffin comes out clean, about 25-30 minutes. Cool in pans for about 10-15 minutes and then transfer muffins onto racks to cool completely .
You can use any combination of berries in this recipe. Frozen berries are fine to use as long as you make sure they are thawed before baking.