Preheat the oven to 180°C.
Flatten the lamb cutlet with a meat hammer.
Pulse bread, lemon zest, herbs, and seasoning in a food processor into crumbs.
Coat the lamb in flour, then egg, and finally the crumb mixture.
Brown the lamb in an ovenproof pan for 3 minutes per side and transfer to the oven.
Roast the lamb for 6 minutes.
Melt butter and fry onions with sugar for 4 minutes until soft.
Add balsamic vinegar and simmer until thick and sticky.
Fry fennel with zest and garlic in a pan for 3 minutes then roast in the oven for 8 minutes.
Plate the onion jam, top with lamb, and serve with roasted fennel.