Line an 8x8 pan with foil; grease with cooking spray and set aside.
In a microwave-safe dish combine semi-sweet chocolate chips and 3/4 cup of sweetened condensed milk.
Microwave on high for 1 minute; stir and put back in microwave, stirring every 30 seconds until completely melted. Mine melted in 1-1/2 minutes.
Pour chocolate mixture into prepared pan and spread it evenly using an offset spatula; set aside.
In a microwave-safe dish combine white chocolate chips and canola oil; melt on high for 1 minute.
Remove from microwave and stir; put back in microwave, stirring every 30 seconds until almost all chips are melted.
Remove from microwave and stir in the rest of the sweetened condensed milk, pumpkin puree, peanut butter and pumpkin pie spice; stir until thoroughly combined.
Pour over previously prepared chocolate layer and spread evenly using an offset spatula.