1. Preheat oven to 350°. Grease muffin tins with melted butter.

2. In the bowl of an electric mixer, cream the butter with the sugar. Add the eggs, one at a time, until well mixed.

3. Combine the milk with the vanilla extract and add to the butter mixture. Beat on low speed to combine.

4. In a medium bowl, whisk together the baking powder and the flours. Combine with the rest of the ingredients in the mixer and beat on low speed until mixed. Fold in the blueberries.

5. Fill muffin cups almost all the way with the batter, then bake in preheated oven until the muffins are light brown on top and a knife inserted in the center of the muffins comes out clean (approximately 22-25 minutes). Cool slightly before serving.