1. Preheat the oven to 350°. Grease 12 regular (½-cup) or 6 large (1-cup) muffin tins or line with paper liners. I find non-stick cooking spray works very well. Combine the cinnamon and sugar for the topping in a small bowl and set aside. In a large bowl, or the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until light and fluffy, about 3 minutes. Add the eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl, then beat in the vanilla.

2. Into a separate bowl, sift both flours, baking soda, baking powder, salt, cinnamon and nutmeg. Add the flour mixture to the batter in three additions, alternating with the buttermilk in two additions, beginning and ending with the dry ingredients. Gently fold in the blueberries. Spoon the batter into the muffin cups to about 2/3 full.

3. Bake in the centre of the oven for 15 to 20 minutes for regular-sized muffins, 25 to 30 minutes for large muffins, or until the tops are golden and spring back when lightly touched and a wooden skewer inserted into the centre of a muffin comes out clean. Cool the muffins in the pan for 5 minutes, then turn out onto a rack. Dip the crowns of each muffin first into the cooled melted butter, then into the sugar-cinnamon mixture, then cool right-side up on a wire rack. Serve warm, slathered with sweet butter, or at room temperature. To store, wrap well in plastic wrap. Muffins may be frozen for up to 1 month.