Preheat oven to 300 degrees F. Combine crackers, melted butter, and 2 tablespoons of sugar. Press into bottom and 1 inch up sides of a 9-inch springform pan; set aside. In bowl, beat 1 package cream cheese with electric mixer until smooth. Beat in peanut butter and 1/4 cup sugar until combined. Fold in 1 lightly beaten egg; set aside.
In saucepan, stir chocolate pieces over low heat until melted and smooth. Remove from heat. Cube remaining cream cheese; add to chocolate. Stir to combine. Stir in milk and vanilla until smooth. Fold in 2 lightly beaten eggs. Spread half the chocolate mixture into pan. Carefully spread all the peanut butter mixture over layer. Evenly spread remaining chocolate mixture.
Bake for 45 minutes or until top is set when lightly shaken. Cool cheesecake in pan on a wire rack for 15 minutes. Use small sharp knife to loosen crust from sides; cool 30 minutes. Remove sides of pan; cool completely on rack. Cover; chill 4 hour. Let stand at room temperature 15 minutes before serving. If desired, sprinkle with peanuts.