ROASTED RED PEPPER DRESSING:
1. First, remove the skin from the monkfish tail: Put the monkfish tail belly-side down on a board. Release some of the skin at the wider end of the tail and pull back so that you can get a sharp, flexible-bladed knife underneath to cut through the fine dorsal spines.
2. Grab hold of the wider and of the tail in one hand and the skin in the other, and briskly pull the skin away, down over the tail.
3. Remove the two fillets by cutting along either side of the thick backbone using a sharp, thin-bladed, flexible knife, keeping the blade as close to the bone as you can.
4. Pull off the thin membrane that encases the fillets, releasing it with the knife where necessary.
5. Cut the fillets across into thin slices and put them into a large, shallow dish.
6. For the roasted red pepper dressing, put the fish stock, vermouth, and saffron into a small pan and simmer until reduced to 3/4 cup (175 ml). Meanwhile, break the roasted red peppers in half and remove the stems, seeds, and skin. Mince the flesh. Mix together the extra virgin olive oil, vinegar, and some salt and pepper to taste.
7. Prepare and light a charcoal fire, or preheat a ridged cast-iron grill pan. Mix together the olive oil, thyme, salt, and some black pepper. Brush the fillets of monkfish with the mixture, place them on the grill or grill pan, and cook for 10 minutes, turning them every now and then.
8. While the monkfish fillets are cooking, return the pan of reduced fish stock to the heat and add the red peppers and olive oil dressing. Bring to a brisk boil and check the seasoning. Whisk in the butter and remove from the heat.