Blueberry Muffins

I am finally getting around to posting this. I took these muffins to my friend, Kristin, this past weekend. They were so good. I loved them so much, I had to make them twice, 2 times in one week. They are that good!
("Bakery Blueberry Muffins" from http://thepioneerwoman.com/tasty-kitchen) I tried another Pioneer Woman recipe before this and I was not happy with the lower fat version that I made. This recipe on the other hand is awesome!

Blueberry Muffins
yield 12 muffins

1/2 cup unsalted butter
1/2 cup granulated sugar
1/2 cup Splenda
1 tspn. vanilla
2 whole eggs
1/2 cup buttermilk, vinegar soured milk
1/2 tspn. salt
2 tspns. baking powder
2 cups flour
1 1/2 cups blueberries, frozen

Preheat oven to 450 degrees. I sprayed a 12 cup muffin tin with cooking spray, and also lined the cups with liners, spraying them lightly also.
Cream together the butter and sugar, then add vanilla, eggs and buttermilk.
In a medium bowl; mix together the dry ingredients. Add the blueberries in, lighty stirring to mix. Add the flour mixture to the butter mixture and stir just until mixed. Do not overmix! Evenly spoon the batter into the prepared muffin cups. If you would like, sprinkle some turbinado/raw sugar on top of the muffins.
Bake for 5 minutes at 450 degrees. Reduce the oven temperature to 375 degrees and bake for another 15-20 minutes, or until a toothpick inserted comes out clean (no gooey batter!).
Let muffins cool to room temperature and serve immediately or serve the next day, if you can wait that long.
I used frozen blueberries the first time I made these, and thawed and rinsed them the second time. You can tell the difference in how blue the first set is.