Preheat oven to 350℉.

1 1½ cups coarsely chopped fresh cranberries

2 Using a pastry blender, cut in butter until mixture resembles coarse crumbs. Stir in 1/2 cup of the chopped walnuts. Set aside.

3 n a large mixing bowl, beat sugar and oil with a whisk. Whisk in egg, vanilla, and buttermilk, stirring until well blended

4 Sift together the remaining 2½ cups flour, the baking powder, baking soda, and salt. Stir into buttermilk mixture using a wooden spoon and stirring just until moistened. 

5 Gently stir in cranberries and the remaining 2 cups chopped walnuts.

6 Lightly coat muffin cups with cooking spray or line with paper baking cups and fill about ¾ full with muffin batter.

7 Sprinkle streusel topping evenly over the top of muffins. Bake about 20 minutes, or until the muffins have risen and the tops spring back when pressed lightly.

8 Cool for a moment in the pans, then remove and serve warm or at room temperature.

Source: California Walnut Board