In small bowl, stir together cereal and melted butter. Press in bottom and up side of ungreased 9-inch pie pan. Refrigerate until set, about 30 minutes. Heat oven to 350 degrees F. Bake crust 15 minutes. Sprinkle with one-third of the chopped chocolate.
Meanwhile, in large heatproof bowl, mix cocoa and remaining chopped chocolate; reserve. In 1-quart heavy saucepan, heat half-and-half over medium-high heat until almost boiling. In medium heatproof bowl, beat sugar, egg and egg yolks with whisk until pale yellow. Slowly beat in half of the hot half-and-half, then pour egg mixture into saucepan. Reduce heat to medium. Heat mixture just to boiling. Cook, beating with whisk, about 1 minute or until thickened. Pour through sieve into reserved cocoa mixture; beat with whisk until smooth. Pour into crust; refrigerate 30 minutes.
Wipe out saucepan. Add 6 tablespoons cream. Heat to boiling over medium-high heat. Place vanilla baking chips and peanut butter in medium heatproof bowl. Pour hot cream on top and let stand until chocolate is melted, about 2 minutes; beat with whisk until smooth. Spread evenly over chilled pie. Refrigerate until firm, about 1 1/2 hours.
To serve, top servings of pie with whipped cream and chocolate shavings.