Line 8 inch square baking pan with parchment paper. In medium saucepan, melt half of the chocolate and 1 T butter over low heat. Remove from heat; stir in 1 c PB, then 2 c cereal. Spread mix evenly in the pan; refigerate until set, about 15 minutes. Wash out saucepan.

In saucepan, combine remaining 2 sticks butter and salt; melt over medium heat, stirring. Remove from heat and stir in remaining PB and sugar. Spread half of PB mix over cereal layer. Top with remaining 1 c cereal. In small bowl, microwave remaining choclate at medium power until melted, 1 1/2 minutes. Stir in remaining PB mix. Spread evenly on cereal topped PB layer; refrigerate until set, about 45 minutes. Cut into pieces.