1. Heat oven to 350°F.
2. Beat cream cheese, sugar and vanilla in mixer bowl until well blended. Add eggs; mix thoroughly. Spread 2 cups batter in crumb crust.
3. Place chocolate chips in medium microwave-safe bowl. Microwave at MEDIUM (50%) 1 minute; stir. If necessary, microwave at MEDIUM an additional 15 seconds at a time, stirring after each heating, until chocolate is melted and smooth when stirred. Cool slightly. Add melted chocolate and milk to remaining batter; blend thoroughly. Drop chocolate batter by tablespoonfuls onto vanilla batter. Gently swirl with knife for marbled effect.
4. Bake 30 to 35 minutes or until center is almost set. Cool; refrigerate several hours or overnight. Drizzle with warmed red raspberry jam, if desired. Cover; refrigerate leftovers. Makes 8 servings.