Brownie Batter Ice Cream Bars

Line a large sheet pan with parchment paper and set aside. In a large bowl, combine brownie mix, butter, espresso powder, and vanilla. Use a hand mixer or wooden spoon to mix. Batter will be thick and similar in texture to cookie dough. Fold in chocolate chips. Dump brownie batter onto parchment-lined sheet pan. Press, using your hands, to flatten, then cover batter with a second sheet of parchment and roll over batter with a rolling pin. Continue to roll until you have an even, thin layer of batter, about 1/4" thick. Freeze for 1 hour. When brownie batter is frozen, remove pan from freezer and halve crosswise. Scoop ice cream over one half and spread with an offset spatula to create a thick and even layer. Place other brownie half on top of ice cream to create a giant ice cream sandwich. Freeze on pan until fully frozen, about 4 hours. Working quickly, slice sandwich into squares. Serve immediately or cover with plastic wrap and place in freezer until ready to serve.