Soup - Cream of Spinach

• 3 qts/3 l water
• 1 lb/500 g spinach
• 2 tablespoon lemon juice 
• 1 tablespoon butter
• 1 teaspoon flour
• 1/2 cup sour cream or yogurt
• salt
• French toast

Wash and pick over the spinach. Set to boil with the water. After boiling for a little while, remove from heat and sieve everything. Set to boil again, adding the lemon juice, salt and butter. Let boil for another minute or two, and then add the sour cream mixed with flour. Serve with French toast.