Combine graham cracker crumbs, 1 teaspoon sugar, and butter; press mixture into bottom of a 9-inch springform pan. Bake at 350° for 8 minutes. Remove from oven; set aside, and cool. Reduce oven temperature to 325°.

Melt morsels according to package directions; set aside.

Beat 3 packages cream cheese at medium speed with an electric mixer until smooth. Gradually add 1/2 cup sugar, beating until blended. Add 3 eggs, 1 at a time, beating well after each addition. Fold in melted chocolate and vanilla. Pour mixture into prepared pan; set aside.

Beat remaining 2 packages cream cheese at medium speed until smooth. Gradually add remaining 1/2 cup sugar, beating until blended. Add remaining 2 eggs, 1 at a time, beating well after each addition. Add peanut butter, beating just until combined. Carefully pour peanut butter mixture over chocolate mixture.

Bake at 325° for 1 hour or until center is almost set. Remove cheesecake from oven; cool on a wire rack. Cover and chill 8 hours or overnight. Gently run a knife around edge of pan, and release sides. Store in refrigerator.