I added the topping on a whim when I made these for the blog, because they look a little plain on photos without it. Combine 3 tablespoons quick cooking oats, 1 tablespoon chopped walnuts or pecans and 1/2 teaspoon pumpkin pie spice in a medium bowl. Cut in 2-3 tablespoons stick butter and mix with your fingertips until small crumbs form. Sprinkle over the muffins just before baking, slightly pressing it into the batter to help it stick.