Beat first 4 ingredients at medium speed with an electric mixer until creamy. Add egg and vanilla; blend well.
Combine flour, soda, and salt; gradually add to butter mixture, beating well after each addition. Stir in 1/2 cup each of semisweet and white chocolate morsels. Spread dough evenly onto 2 lightly greased 6-inch round pizza pans.
Bake at 375° for 20 to 25 minutes or until lightly browned. Working quickly, sprinkle crust with remaining semisweet and white chocolate morsels; drop peanut butter by tablespoonfuls onto crust. Let stand 5 minutes or until morsels and peanut butter are softened; gently spread evenly over crust. Decorate with desired toppings; drizzle pizza with melted white chocolate.
NOTE: One lightly greased 12-inch pizza pan may be substituted.