01 - Set oven to 350°F (175°C) and allow to fully preheat.
02 - Combine brownie mix with eggs, oil, and water in a mixing bowl according to package instructions. Stir until smooth.
03 - Place mini graham cracker pie crusts onto a rimmed baking sheet for stability.
04 - Spoon brownie batter into each prepared crust, filling no more than two-thirds full to allow space for rising.
05 - Bake in preheated oven for 20 to 25 minutes, or until a toothpick inserted into the center yields a few moist crumbs.
06 - Remove pies from the oven. Evenly distribute mini marshmallows and chocolate chips over each warm brownie pie.
07 - Return baking sheet to the oven and bake for an additional 3 to 5 minutes, until marshmallows are puffed and lightly golden.
08 - Transfer pies to a rack and cool for 10 to 15 minutes before serving. Enjoy warm or at room temperature.