Beat 1/2 cup butter in small bowl until fluffy. Gradually add 1/2 cup maple syrup and beat until well blended. (Maple butter can be prepared 2 days ahead. Cover and refrigerate. Bring to room temperature before using.)

Preheat oven to 375 deg F. Line twelve 1/2 cup muffin cups with muffin papers. Combine walnuts and 3 tablespoons maple syrup in small bowl; set aside.

Sift flour, sugar, baking powder, baking soda and salt into medium bowl. Mix in cornmeal. In separate bowl beat buttermilk, eggs, melted butter and remaining 1/4 cup maple syrup to blend. Add egg mixture to dry ingredients, stirring just to combine. Do not overmix.

Divide batter among prepared cups. Spoon some maple-walnut topping over each muffin, dividing evenly. Bake until tester inserted into centres of muffins comes out clean, about 20 minutes. Remove muffins from pan and cool 15 minutes. Serve warm with maple butter.