1) Clean the pheasants.
2) Chop two of the onions and the birds' livers.
3) Put half the mixture in each pheasant.
4) In a skillet, heat oil and butter together and brown birds all over.
5) Put the birds into a casserole.
6) Remove mushroom stalks and cook in the remaining fat with the wine, until liquid is reduced by half.
7) Mix flour with a little butter and add to the gravy to thicken it, and pour over the pheasants.
8) Cook onions in boiling salted water until tender, drain and add to casserole.
9) Toss mushrooms in butter and add to other ingredients.
10) Cover the casserole and cook at 325°F, 170°C, Gas Mark 3, for 1 hour.
11) Let it cool.
12) In rigid plastic container or in foil tray, pack the birds.
13) Keep in freezer until used.
14) Birds can also be eaten immediately once cooked.
15) To serve: thaw the birds, heat them through and serve as main dish.