Place chocolate morsels, 1/2 cup corn syrup, and butter in a 2-quart casserole.
Microwave at HIGH 2 to 3 minutes.
Stir well after 1 minute.
Stir in 2 cups of cereal.
Press mixture into a buttered 9-inch square pan.
Combine remaining corn syrup, peanut butter, vanilla, and salt in the 2-quart casserole.
Microwave at HIGH 1 1/2 to 2 minutes.
Stir after 1 minute.
Stir in remaining cereal.
Spread over the chocolate mixture.
Cool slightly and chill at least 1 hour before cutting.