Combine cracker crumbs and quarter cup melted butter, press mixture evenly onto bottom of a 23 cm springform pan. Set aside. Peel, devein, and chop shrimp. Cook shrimp and next 4 ingredients in 3 tablespoons butter in a large skillet over medium-high heat, stirring constantly, 4 to 5 minutes or until shrimp are done and vegetables are tender. Drain well and set aside. Beat cream cheese and mayonaise at high speed of an electric mixer until creamy; add eggs, one at a time, beating after each addition. Gradually add milk, beating well at low speed just until blended. Stir in shrimp mixture, Gruyere cheese, and white pepper. Pour mixture into prepared pan. Bake at 150ºC or 1 hour and 20 minutes or until set. Turn oven off, and partially open oven door; leave cheesecake in oven 1 hour. Cool completely on a wire rack; cover and chill at least 8 hours. Serve with warm Italian Tomato sauce. Garnish with sweet red pepper strips, whole shrimp, and fresh basil sprigs if desired. Italian Tomato Sauce directions: Cook onion and garlic in oil in a large skillet over medium-high heat, stirring constantly, until tender. Add tomatoes and remaining ingredients; bring to a boil. Reduce heat, and simmer, uncovered, 20 minutes or until most of liquid evaporates; stirring occasionally. Remove and discard bay leaf.