If you don’t have mashed potatoes, peel and boil potatoes equal to one-half of the total weight of your broccoli. For instance, if you have 500 grams of broccoli, then you use 250 grams of potatoes. Puree the potatoes along with the broccoli, garlic and onion. After pouring the contents of the blender into the pot, add four tablespoonfuls of butter and a cup of sour cream to the soup. Season with salt and pepper, stir, heat until simmering then serve.