Trim venison steaks, removing all fat and gristle; pound with a meat tenderizer until steaks thin but not tearing.

Combine flour, bay leaf, salt, and pepper in a shallow bowl. Dredge steaks in flour mixture until evenly coated.

Heat 1 tablespoon olive oil in a large heavy skillet over medium heat. Sauté onions until soft and translucent. Stir in mushrooms and garlic; cook until tender. Transfer to a plate; set aside.

Heat remaining 3 tablespoons oil in same skillet; fry steaks until golden brown, about 2 minutes per side. Return mushroom mixture to skillet; stir in gravy and milk. Reduce heat, cover, and simmer for 30 to 40 minutes, stirring occasionally to prevent sticking.