Preheat the oven to 350ºF. Butter or spray an 8x8 inch glass baking dish with nonstick cooking spray.
In a large bowl, stir together the brownie mix, oil, espresso, and eggs. Add 1/4 cup of the chocolate chips and stir until combined.
Pour 1/2 of the batter in the glass baking dish. Arrange the Snicker squares evenly over the batter. Pour the remaining half of the batter over the Snicker squares. Sprinkle the remaining 1/4 cup of chocolate chips evenly on top.
Bake in the oven for 1 hour. Check with a toothpick--may need to continue baking for an additional 5-10 minutes. I left mine in for 5 more minutes.
Allow to cool completely before cutting into squares and serving.
Notes
* Strongly brewed coffee or water can be used in place of the espresso.