For the monkfish, heat a frying pan over a medium to high heat, add the butter, onions and garlic and cook for 2-3 minutes, or until softened. Transfer the mixture to a bowl and set aside to cool slightly.
Stir the sausage meat, egg, lemon zest, sage and breadcrumbs into the onion and garlic mixture until well combined. Season with salt and freshly ground black pepper.
Lay the monkfish fillets onto a chopping board and, with a sharp knife, cut a small hole in the side of each fillet to create a 'pocket'.
Carefully fill the holes with the stuffing and wrap the monkfish fillets tightly in the strips of bacon.
Wrap each monkfish fillet tightly in heatproof cling film and chill in the fridge for 30 minutes.
Once chilled, poach the monkfish fillets in a pan of simmering water for 15 minutes.
Remove the poached monkfish fillets from the water using a slotted spoon and set aside to rest for five minutes.
When the monkfish fillets are cool enough to handle, carefully remove the cling film, reserving any cooking juices.
Heat the olive oil in a frying pan over a medium heat and fry the fish for 1-2 minutes on each side, or until golden-brown on both sides. Add a knob of butter and the reserved cooking juices and continue to cook until the butter has melted.
Meanwhile, for the roast vegetables, boil the potato cubes in a pan of boiling water for 5-10 minutes, or until almost tender. Drain well.
Heat the rapeseed oil in a frying pan over a medium heat and fry the potato cubes for 2-3 minutes, stirring well, until golden-brown on all sides. Add the blanched Brussels sprouts and fry for a further 4-5 minutes.
Add the chestnuts, sage and butter and season with salt and freshly ground black pepper. Continue to fry the mixture until everything is warmed through, golden-brown and well combined. Drain off any excess butter.
For the dressing, heat the butter in a frying pan and cook the garlic and sage leaves for 1-2 minutes, or until the butter turns brown and the sage leaves are crisp. Remove the pan from the heat and set aside until the white solids from the melted butter have risen to the top of the butter.
Strain the sage butter mixture, reserving the liquid butter.
Meanwhile, bring the port, red wine vinegar, red wine, shallots and sugar to the boil in a saucepan. Reduce the heat to a simmer and continue to cook until the sauce has reduced to a syrup.
Stir in the strained liquid butter, cranberries, sage and garlic and season with salt and freshly ground black pepper. Continue to simmer the mixture until the cranberries have softened slightly.
To serve, spoon the roasted vegetables into the centre of four serving plates. Slice the stuffed monkfish fillets into three pieces and place them on top of the vegetables. Spoon over the reserved cooking juices from the pan the monkfish was cooked in, and the cranberry dressing.