Things You'll Need
Milk or cream
When making tomato soup, many people try to add the cream the wrong way, resulting in curdling or other unpleasant texture effects. Besides adding the cream the right way and at the right time, it is also important that you use a heavy bottomed pot to avoid uneven heat conditions. While many people like to use cream, you can also use milk with this technique, as you are thickening it further by using flour and butter anyway.
Keep the tomato soup that you wish to add the cream to over low heat to keep it hot.
Combine equal parts of melted butter and flour in a bowl. Use one tablespoon per cup of tomato soup.
Slowly whisk in some cream or milk, about 1/4 cup per cup of tomato soup.
Stir the cream mixture into the hot soup until combined. The soup should lighten a shade or two and the consistency should be nice and thick.