Instructions

1. Melt butter in a small saucepan over low to medium heat to make a roux. Incorporate an equal part of flour, whisking and cooking the mixture until the flour loses its floury aroma. Stir constantly and thoroughly to keep the butter from browning and to blend the two ingredients into a smooth paste.

2. Add broth or cooking liquid to the flour-butter mixture, stirring constantly. Cook over low to medium heat until a smooth sauce results. Use about 1 tablespoon each of flour and butter to about 2 cups of broth.

3. Pour the roux slowly into the cooked potato soup, stirring until it is evenly distributed throughout the pot. Continue stirring gently over low to medium heat until the soup thickens. At this point, the soup has the desired thickness, but it may seem grainy, lacking a smooth and creamy texture.

4. Slowly pour cream or half-and-half into the thickened soup, stirring to incorporate it as you pour. Higher fat dairy provides a creamier texture, but you can use whole, 2 percent or skim milk with good results. Each gives slightly different results because of the differences in fat content. Using a roux adds a little fat from the butter, which you can adjust to balance lower-fat milk.

5. Add the dairy just before serving. Don’t boil the soup after adding the dairy; the heat can affect the protein structure and cause separation. If the soup cools from the dairy addition, reheat it over low heat just until it's at serving temperature, stirring constantly. Keep the temperature below 180 degrees Fahrenheit to prevent separation from heat.