Saute Onions And Leeks In Butter Until Very Soft And Brown, About 30 Minutes. Sprinkle With Sugar And Saute For 5 Minutes. Add Soy Sauce. Simmer For 1 Minute. Add Tomatoes, Tomato Paste, Stock, Salt And Pepper. Simmer For 30 Minutes. Place In Individual Oven-Proof Serving Bowls. Sprinkle With Grated Cheese And Bake Under The Broiler Until The Cheese Is Starting To Brown. Serve.