Preheat oven to 325 degrees. Mix brownies as directed on box. Pour into a 9x13 pan and bake for 25 minutes. Let them cool on the counter for about 20 minutes, then put into the fridge for another 15. (I did this to speed it up.)
While brownies are cooling, mix together the PB Truffle ingredients with a mixer. Spread over the cooled brownies.
Microwave the chocolate and oil for 30 second intervals, stirring until melted. Pour over the peanut butter mixture and spread it out. Place in fridge for at least 2 hours or overnight.