In a large bowl mix together the brownie mixes, oil, water, and eggs until well combined.
Spread half of the brownie batter on the bottom of the prepared pan.
Top with a layer of the peppermint patties.
Spread the remaining brownie batter over the peppermint patties.
Bake in the preheated oven for 50-53 minutes. A toothpick should come out of the middle relatively clean.
Cool at room temperature for at least one hour. I like to cool completely in the refrigerator for a couple of hours after, too. You can definitely enjoy them warm out of the oven, they will just be a little gooey!
Cut and enjoy!
Notes
Storage - store brownies in an airtight container at room temperature for 2-3 days or in the refrigerator for 4-5 days.