Heat half the butter and olive oil in a small fry pan.
Add the venison fillets and fry, over a high heat, for one minute.
Turn the steaks over and fry for a further 3-4 minutes (longer if you like medium to well done fillets).
Pour in the brandy and when the flame has died, remove the fillets from the pan and arrange on a warm plate.
Pour in the crème de cassis and the stock and season well. Leave over the heat until the sauce has thickened and reduced.
Meanwhile, form a small patty by combining the sausage meat, cranberries and chestnuts.
Heat the remaining butter and oil in a small fry pan. Add the patty and fry for 2-3 minutes, either side.
Finish the croutons by spreading them with pâte, then the red current jelly.
Pour the crème de cassis sauce over the venison.
Add the patty and croutons to the plate, garnish with a sprig of watercress and serve.
