Turn oven on 425ºF.
Combine pork with sage, fennel, garlic, grated onion, salt, pepper and cheese. Form 8 patties.
Combine fennel wedges, potatoes and onions with 1/4 cup EVOO, salt and pepper. Roast 35-40 minutes turning once until tender and the potatoes are crispy.
Combine chicken stock, vinegar and brown sugar in a small pot over medium-high heat and bring up to a bubble. Reduce the heat to medium and cook until reduced by about half and thick and syrupy, about 10 minutes.
Heat about a tablespoon EVOO in large skillet or on griddle and cook patties 7-8 minutes turning once.
Serve 2 patties with roasted fennel, potato and onions alongside with some balsamic drizzle over the top of the dish.