Green sauce:
To finish:
In a small saucepan gently fry the anchovies in their olive oil for 2 minutes or so until they have totally collapsed, you will see this happen when you stir them with a spoon.
Add the garlic, lemon zest and pepper before pouring in the wine.
Heat up to a simmer, then turn off the heat and allow it to cool. Marinate the venison fillet in this for 4 hours.
In the meantime, make the green sauce. Combine the tarragon, marjoram, capers, shallot, lemon juice, olive oil and garlic together to form the sauce. Season with salt to taste.
Over a hot griddle or barbecue sear the venison fillet for 3- 4 minutes on each side, painting occasionally with the marinade. They should be well coloured on the outside and pink within.
Toast the bread (preferably using a barbecue) and spread he mustard over 4 slices. Slice the venison and lay it on top.
Apply green sauce and remaining slice of toast and eat immediately.