Heat a frying pan over medium heat, add half the butter, then bacon and shallots, and stir occasionally until shallots are tender (5-10 minutes). Remove from pan, add duck liver and remaining butter and turn occasionally until browned and cooked medium-rare (2-3 minutes). Remove livers from pan and set aside. Add shallot mixture and port and cook until syrupy (3-5 minutes), then add veal stock and cook until reduced to sauce consistency (5-10 minutes). Return livers to the pan, season to taste and keep warm.
Meanwhile, preheat a grill on high heat. Combine frisée and radicchio in a bowl, drizzle with olive oil and red wine vinegar and set aside. Place bread on an oven tray and toast until golden (1-2 minutes each side). Serve toast topped with liver mixture and salad and drizzled with extra pan juices.