Blueberry Streusel Muffins

[ezcol_1half] Ingredients Streusel 1/2 cup packed brown sugar 1/2 cup walnuts, chopped 1 teaspoon ground cinnamon Muffins 1/2 cup unsalted butter softened 1/2 cup granulated sugar 1/4 cup packed light or dark brown sugar 2 large eggs, room temperature preferred 1/2...