Pumpkin Streusel Muffins

Name: Pumpkin Streusel Muffins
Ingredients: ¼ cup (½ stick) chilled unsalted butter, cut into pieces; ¼ cup (packed) light brown sugar; 2 tablespoons all-purpose flour; 2 tablespoons whole wheat flour; ½ teaspoon kosher salt; ¾ cup walnuts, chopped, divided; Nonstick vegetable oil spray (optional); 1¼ cups all-purpose flour; ½ cup whole wheat flour; 2 teaspoons baking powder; 1 teaspoon ground cinnamon; 1 teaspoon ground ginger; 1 teaspoon kosher salt; ¼ teaspoon ground allspice; ¼ teaspoon ground nutmeg; ⅛ teaspoon ground cloves; 2 large eggs, room temperature; 1 cup (packed) light brown sugar; 1 cup canned pure pumpkin; ½ cup virgin coconut oil, warmed, slightly cooled