For the classic French lentils, heat a sauté pan or a large frying pan and then add the butter and oil. Once hot, add the onion and cook for two minutes. Add the garlic, diced pancetta, carrot, celery, leek and bay leaf and cook for a further two minutes.
Add the lentils and red wine and bring to the boil. Cook until the volume of wine has reduced by half, then add the stock and cook the lentils for 25-30 minutes. Mix in the sherry vinegar and parsley.
For the monkfish, season the monkfish fillets with salt and freshly ground black pepper.
Heat a frying pan until smoking, add the olive oil and monkfish and cook on each side for 1-2 minutes, or until the crust is golden-brown and the fish is cooked through. Remove from the pan and rest on a warm plate for 2-3 minutes, then thickly slice into four pieces.
To serve, place a spoonful of the lentils in each of four shallow serving bowls and place the sliced monkfish on top. Garnish with the sliced cooked pancetta and the parsley cress.