Marinate venison in red wine, port, herbs, and spices in the fridge overnight.
Preheat the oven to 140°C.
Drain meat, reserving marinade, and brown in a hot pan with oil.
Cook bacon and vegetables in the pan until lightly browned.
Add marinade, reduce by two-thirds, return meat, and add 2L of stock.
Cover the surface with greaseproof paper and bake for 2 to 3 hours.
Sieve cooking juices and reduce until the sauce is rich and dark.
Increase oven to 170°C.
Bake squash and beetroot in a foil parcel with herbs and vinaigrette for 40 minutes.
Brown halved pears in half of the butter for 10 minutes.
Add remaining stock to pears, bubble briefly, then set pears aside.
Blanch parsnips, then pan-fry in remaining butter until golden.
Return venison and chestnuts to the sauce to warm through.
Serve casserole shanks with roasted vegetables and pears.