- 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.