Heat your oven to 190°C/Fan 170°C/Gas 5. Scrub and peel the potatoes. Roughly chop them into 2cm chunks and add them to a roasting tin. Drizzle over 1 tbsp olive oil. Season with a pinch of salt and pepper. Turn to coat in the oil.
Halve the red onions, leaving them in their papery skins. Add them to the tin, cut-side up. Roast the veg for 30 mins.
Put 1 tsp fennel seeds in a mortar and pestle. Grind to make a fine powder. Add 4 juniper berries. Peel and roughly chop the garlic clove. Add them to the mortar and crush them in with the fennel seeds to make a thick paste. No mortar and pestle? Use a small bowl and the end of a rolling pin or the bottom of a jam jar.
Finely chop the rosemary leaves. Add them to the spice paste with a pinch of salt and 2 tsp oil. Stir together. Put the venison steaks in a dish and rub in the juniper marinade, making sure they are well covered. Set them aside to marinate for 15-20 mins.
Dice the dried figs, discarding the woody bits. When the potatoes and onions have roasted for 30 mins, scatter the figs into the tin. Drizzle a little balsamic over each onion half. Roast for another 15 mins, till the potatoes are golden and the onions are a little charred and soft.
Warm a griddle or frying pan for 2 mins over a high heat. Add the venison steaks. Fry for 2-4 mins on each side till the steaks are browned and cooked to your liking (cook them for longer if the steaks are thick or if you prefer well-done meat).
Put the steaks on a board or warm plate and loosely cover with foil. Let them rest for 5 mins.
While the steaks rest, shred the cavolo nero leaves and add to the steak pan with a splash of water. Cook and stir for 3-4 mins to just wilt them.
Slice the steaks and serve them with the roast veg, figs and cavolo nero.