Combine all of the ingredients in a large bowl and mix thoroughly until well combined
Spray a 9x9 inch square cake pan with cooking spray. Line the pan with parchment or wax paper with a couple of inches of overhang. Spray the top of the paper with cooking spray as well.
Press the mixture into the pan and flatten the top.
Chill in the refrigerator for at least 2 hours.
Use the parchment paper overhang to help remove from the pan.
Cut into slices, wrap each slice in wax paper and store in the refrigerator