Prepare the pheasant first. Pheasant legs have tough tendons that need to be removed before cooking. Using a pair of pliers, tug hard on the exposed ends of the tendons (at the foot end), and pull them out.
Cut the legs and thighs away from each bird, but leave the breast meat attached to the ribcage. Cut away the backbone using strong kitchen scissors or poultry shears.
Place the flour onto a plate and season with salt. Dust the skin of the pheasant with the flour, shaking off any excess.
Preheat the oven to 200C/400F/Gas 6.
Heat a large frying pan until hot, then add the oil and knob of butter. Fry the legs and breast meat, skin-side down, until browned on all sides (don't crowd the pan - if necessary, fry the meat in batches). Set the breast sections aside on a plate and put the legs in a roasting tray.
Put the pheasant legs into the oven to roast for 5-7 minutes. Add the breast sections, skin-side up, then continue to roast all the meat for another 10-12 minutes. Remove from the oven onto a warm plate, reserving the cooking juices, and loosely cover the pheasant with foil. Allow to rest for five minutes.
Meanwhile, make the sauce while the pheasant is roasting. Into the same pan as the pheasant cooking juices, add butter the shallots, thyme and a little salt. Cover and cook gently for 10 minutes until the shallots have softened. Then add the garlic and fry for another minute.
Pour in the wine, turn up the heat and boil the sauce furiously until the wine has evaporated away to leave no watery liquid. Add the cider or white wine vinegar and continue to cook until the liquid has disappeared.
Pour in the stock and continue to cook, reducing the liquid to about a third of its original volume.
Add the mustard and stir in the cream. Return to the boil then simmer for a few minutes until the sauce is just thickened. Add the reserved cooking juices and season, to taste, with salt and freshly ground black pepper.
Carve the pheasant breast from the ribcage (it should still be a little pink). This will give two pieces of breast from each bird. Cut into thick slices.
To serve, arrange Puy lentils on each of four plates, spoon over a generous amount of sauce, then top with one sliced breast and a leg per plate. Sprinkle over a little chopped curly leaf parsley.