Heat your oven to 190ºC/Fan 170ºC/Gas 5. Halve the squash. Scoop out the seeds. Use a knife to make a criss cross pattern in the flesh. Season. Place, cut-side up, on a baking tray. Rinse the thyme. Add a sprig to the hollows of the squash halves. Roast for 40 mins till soft.
Pop the venison in a bowl. Peel and chop the garlic. Add to the bowl with 1 tbsp olive oil, some pepper and a few pinches of the thyme leaves. Crush the juniper berries with the back of a teaspoon. Add 4 of them to the venison. Turn to coat. Set aside.
Cut the butter into 3 portions. Fill a kettle and boil it. When the squash is nearly ready, fill a pan with hot water. Bring to the boil. Halve the cabbage. Finely shred and rinse one half. Pop in the pan. Boil for 4-5 mins till tender.
Crumble the stock cube into a measuring jug. Pour 200ml of the cabbage water into the jug. Drain the cabbage. Pop it back into the warm pan. Add a portion of the butter. Season. Take the cabbage out of the oven and turn it off. Tip into a serving dish. Put it back in the oven to keep warm.
Using 2 large spoons, scrape the hot squash out of its skin. Tip into the cabbage pan. Add a portion of the butter and some seasoning. Mash till smooth. Add to the cabbage in the oven.
Melt the last of the butter in a small pan. Add 1 tbsp of the flour. Cook, stirring, for 1 min. Stir in the remaining 4 juniper berries and a pinch of the China 5 spice. Gradually whisk in the hot chicken stock. Simmer very gently for 2-3 mins till thick.
Heat a small frying pan. Shake the garlic and thyme off the venison. Add the steaks to the pan. Fry for 2-3 mins each side for medium-rare, longer if they are thick or you prefer you steaks more well done. Pop on warm plates.
Add 100ml hot water from the kettle to the hot frying pan. Bubble for 30 secs to deglaze the pan. Add the pan juices to the gravy pan and stir in. Serve the venison with the butternut mash, cabbage and the gravy.