Whole Wheat Banana Oat Muffins
1 cup rolled oats 1 cup walnuts, crushed using a rolling pin 1 teaspoon baking soda 2 eggs 2 teaspoons baking powder 3 extra-ripe bananas, mashed ¼ cup brown sugar, packed ¼ cup white sugar ¼ teaspoon ground nutmeg, or more to taste ½ teaspoon ground cinnamon, or more to taste ½ teaspoon salt ½ teaspoon vanilla extract ¾ cup all-purpose flour ¾ cup milk ¾ cup whole wheat flour ⅓ cup vegetable oil