Banana Refrigerator Cake with Dreamy Creamy White Chocolate Frosting

My favorite banana cake is made with oil instead of butter. Though I adore the flavor and softness of the butter version, the crumb becomes hard and dense when refrigerated. Oil keeps the cake extra moist and tender, even when served cold, a delicious way to eat it, especially, with its luxuriously creamy, absolutely delicious white chocolate frosting, which requires refrigeration. If you use crème fraîche instead of sour cream in the batter, the flavor will be more mellow and the te