Mince the onion and finely chop the garlic. Slice the chorizo.
Heat a drizzle of oil in an ovenproof pan. Fry the onion and garlic for a few minutes until the onion is soft and lightly browned, then add the cayenne pepper, chorizo and cherry tomatoes. Mix well and cook for a further 2 minutes.
Deglaze with the chicken stock (or white wine) and add the monkfish to the centre of the pan. Season with salt and pepper, add the thyme and cover.
Place in the oven and cook for 25 minutes, basting the monkfish from time to time with the cooking juices.
Meanwhile, cut the new potatoes in half and season with olive oil, rosemary, salt and pepper.
Place the potatoes on a baking tray covered with parchment paper or silicone and bake for 20 minutes or until crisp and golden brown. Stir occasionally.