In large mixing bowl cream butter with both sugars until very light in color. Scrape sides of bowl with rubber spatula. Add vanilla, eggs and buttermilk, beating constantly. In another bowl stir together nutmeg, baking powder, baking soda, salt and flours. Add to butter mixture. Gently mix just until combined. Gently fold in blueberries. Fill paper-lined muffin cups to top with batter. Sprinkle each muffin with about 2 teaspoons nutmeg sugar. Bake on rack in upper 1/3 of 400-degree oven until muffins are lightly browned, about 20 to 25 minutes. Remove muffins from pan to cooling rack. Serve warm or at room temperature. Makes 16 muffins or 6 jumbo muffins.