Follow this quick recipe for some delicious lentil soup, made from scratch. To make a delicious stove top lentil soup, you will need the following ingredients: 1cup of lentils, 4 cups of water, 1 onion, 1 tsp oil, salt and pepper, butter and flour. Boil the lentils in water. Chop the onion, and fry the onions with the lentils in the oil. Add 4 cups of water and bring to a boil. Put the butter in a pan, melt it, and add the flour. Add some cold water to the pan and stir. Pour it into the soup. Add salt and pepper and cook for 5 minutes.