- 1 1/2 pounds leeks, sliced
- 1 onion, chopped
- 1 potato, cubed
- 1 carrot, chopped
- 1 tablespoon margarine
- 1 tablespoon olive oil
- 1 1/4 teaspoons dry mustard powder
- 2 teaspoons cornstarch
- 1/2 cup water
- salt and pepper to taste
- 1 teaspoon white sugar
- 5 cups water
- 1 cube vegetable bouillon
- 1 cup heavy whipping cream
- 1/8 cup shredded Gruyere cheese
- 1/4 cup shredded Cheddar cheese
In a large pot over medium heat, saute the leeks, onion, potato and carrot in the butter or margarine and the olive oil for 10 minutes, or until all vegetables are tender.
Mix the mustard powder and cornstarch with the 1/2 cup water to make a thin paste. Set aside.
Season the vegetable mixture with salt and pepper and sugar. Stir in the mustard-water mixture and the 5 cups water. Bring mixture to a boil. Stir in the bouillon cube, reduce heat and simmer for about one hour, until reduced by half.
Using a hand blender or upright blender, puree mixture until frothy but not completely smooth.
Return this to the pot and bring to a boil. Stir in the heavy cream, Gruyere and Cheddar cheeses. Heat until cheeses melt, do not boil. Serve hot.