Preheat oven to 350°F. Grease muffin tin or fill with liners. Sift together both flours, salt and baking powder. In a larger bowl, cream butter, sugar and vanilla until fluffy. Add eggs, one at a time, blending well after each. Add milk. Reduce the speed to low and gradually add the flour until all is mixed in, but do not overmix. Fold in blueberries. Fill muffin cups 3/4 full. Bake for 25-30 minutes. Cool for 10 minutes in the muffin tin and then turn out onto wire racks to complete cooling.