Difficulty:[usr 2]
Mark the stock of lamb, that is to say, remove the fillets from the racks of lamb, crush the bones, put them in a saucepan with the oil, brown and add all the washed and peeled ingredients of the stock.
Stir, moisten with white wine, reduce completely, then moisten up to the water level, cook for 18 minutes, filter through a sieve, degrease and set aside.
Trim the lamb fillets, salt and pepper.
Put 2 knobs of butter in the pan, sear them for a minute on each side and finish cooking in the oven for 10 minutes.
Reserve the fillets, discard the cooking butter and moisten with the lamb jus.
Open and drain the tins of flageolets, brown them separately in 2 knobs of butter with the chopped shallots.
Salt and pepper.
