Crush enough black peppercorns to give your venison a light coating, don't make them too fine or the flavour will be overpowering. Finely chop enough dried mugwort to do the same. Mix the mugwort and pepper together and roll your venison in it, giving a light coating. Leave in the fridge over night or if it is less than 2 hours before you cook the venison, leave it out on the side. If you do refrigerate the meat then make sure you take it out in good time for it to be at room temperature when you cook it.
To make the rosti, bring a saucepan of water to the boil then add the potatoes, cooking for 5 minutes. Drain and allow to cool before grating with a cheese grater. Grate in some horseradish root to taste then season with salt and pepper.
In a frying pan over a medium heat, warm a little oil. Form the grated potato into patties and fry on each side until golden brown and tender, about 12 minutes. Remove from the pan and keep warm.
To cook the venison, warm a little vegetable oil in a frying pan over a high heat until just smoking. Season the venison meat with salt then add to the pan.Turn each piece as it colours - be careful not to let the pepper burn too much - and keep turning until the meat is well coloured. If you are cooking the meat to rare, small steaks will take a matter of 2 or 3 minutes each side while larger ones will take under 10 minutes. Once cooked to taste, rest the meat for at least as long as it cooked for in a warm place and then slice across the grain.
To make the blackberry sauce, press the blackberries through a sieve or run through a mouli. Deglaze the pan in which the steaks were cooked by adding the wine and stirring over a high temperature, allowing it to reduce. Add the sloe gin, blackberry puree, blackberry jam and bring to the boil until the sauce coats the back of a spoon. Add seasoning and sharpen with a squeeze of lemon juice.
To serve, place the potato rosti on a plate with the sliced venison steak. Spoon over the blackberry sauce and serve with wild cabbage or sea beet.
If you cannot source venison, use some good quality beef fillet steaks.
If you have problems with the mix falling apart try adding a little flour or egg.