cream of cauliflower soup with gruyere cheese

Ingredients

• 2 tablespoons vegetable oil
• 2 - leeks, chopped
• 1 1/2 cups onions, chopped
• 1 1/2 cups celery, chopped
• 1 tablespoon garlic, crushed
• 1 tablespoon fresh thyme, or 1 tsp dried
• 3 pounds cauliflower, small florets
• 4 cups chicken broth
• 1 cup whipping cream
• 1 1/2 cups gruyere cheese, finely grated
• pinch cayenne
• - chives, finely chopped