Blueberry Buttermilk Muffins

This is my adopted recipe Feb 2005 I didn't change the recipe ingredients because 11 members found it good the way it was. I did add 1 teaspoon vanilla as suggested by 1 reviewer. I used 1/2 cup canola oil instead of butter. 2 heaping cups frozen blueberries mixed with a little of the flour mixture to make sure they didn't stick together. I made 6 giant muffins. Very good muffins. I had to bake mine for 35 minutes, they were so big.