Use a meat mallet to pound the backstrap pieces to 1/4" thickness. Season each piece with salt and pepper and set aside.
Place your flour, beaten egg, and breadcrumbs in three separate, shallow dishes in an assembly line fashion. Flour, then egg, then breadcrumbs.
Heat the olive oil in a large skillet over medium-high heat.
Dredge each of the venison pieces in the flour, shaking off any excess, then in the egg, and finally in the breadcrumbs, making sure to coat each side well. Place carefully into the pan and cook for 2-3 minutes, until nicely browned, then flip and cook another 2-3 minutes, or until cooked through. You don't want to overcook and dry them out, so keep a close eye on them.
When the venison is mostly cooked through, top with a few spoonfuls of marinara sauce and a slice (or two) of mozzarella. At this point you can either place a lid on your skillet to help the mozzarella melt, or pop it in your broiler for a minute or so. Top with basil, if you like and serve over spaghetti with your favorite veggie and some good, crusty bread!