Prepare the marinade and the moose steak 4 days before you will cook it.
Pour the red wine in a bowl.
Add the mustard, olive oil, the black peppercorns in the bowl and stir.
Put the moose steak in a plastic bag for cooking, keep the net on the steak.
Add the marinade and the onion in the bag. Make sure the meat have marinade on all sides.
Press out the air from the bag and close it.
Put the bag in a bowl in the fridge for 4 days. Every day flip the bag upside down.
The day of cooking the dish:
Start the oven at 175 degree Celsius
Take out the moose steak and put it in a oven form. Still keep the net on the steak.
Pour the marinade on the meat and in the oven form.
Put a oven thermometer in the thickest end of the steak.
Put the steak in the middle of the oven.
Take out the steak when the temperature in he meat reach 70-75 degree Celsius.
Sauce and potatoes
Put aluminum foil around the steak, and put it on the bottom part of the oven for 30 minutes.
While the steak is covered by aluminum foil in the oven, it is time to prepare the rest och the dish.
Boil the potatoes in a casserole.
Fry the chanterelle mushrooms with 2 tablespoons of butter.
Put 2 tablespoons of butter in a casserole.
Add the flour in the casserole and stir.
Lower the heat and add the cream and stir.
When the sauce start to bubble add the chanterelles, the salt and the black pepper and stir.
Cut really thin slices of the meat and serve it warm on a plate together with the potatoes and the sauce .