Heat oven to 300 degrees F. Line a 9 x 13-inch baking pan with
heavy foil; set aside.
Combine crumbs and butter; press firmly on bottom of foil-lined pan.
With mixer, beat cream cheese in large bowl until fluffy. Gradually
beat in sweetened condensed milk until smooth. Add eggs and
vanilla extract; mix well.
Pour half of the batter evenly over prepared crust. Stir melted
chocolate into remaining batter; spoon over vanilla batter.
With a table knife or metal spatula, gently swirl chocolate
batter through vanilla batter to marble.
Bake for 45 to 50 minutes or until set.
Cool. Chill for at least 1 hour.
Use foil to lift out of pan. For hearts, cut with heart-shaped
cookie cutter; or with a knife, cut around wax paper heart shape.
Or cut into bars.