Good-Cooking - Boston Cream Cheesecake

Ingredients

• 1 (9 ounce) yellow cake mix (one layer size)
• 16 ounces cream cheese (at room temperature)
• 1/2 cup granulated sugar
• 1 teaspoon vanilla extract
• 2 eggs
• 1/3 cup sour cream
• 2 squares unsweetened chocolate
• 3 tablespoons butter or margarine
• 2 tablespoons boiling water
• 1 cup confectioners sugar