When using an assortment of beans that are different sizes, it is best to blanch each type separately in order to control the cooking time of each. If preparing beans ahead of time, remove them from the hot water, and transfer to an ice bath until completely cool. Drain in a colander, and store them in a clean towel. When ready to serve, drop beans all at once into boiling water until heated through, 1 to 2 minutes. Drain and proceed with the recipe.