Roast the bones marrow in a 225C oven cut side up for 10-15 minutes until the marrow is soft and beginning to bubble.
Scoop out the marrow and place in the fridge.
While the marrow is roasting, stew the venison. Heat the olive oil in a large pan over high heat.
Season the venison with salt and pepper. Add the venison to the hot pan and sear all sides until brown and caramelized.
Add the shallot, carrot and celery and cook for 2-3 minutes occasionally stirring.
Add the port and stir in the tomato paste.
Add the thyme, bay leaf and stock. Cover and transfer to the oven at 150C and cook until fork tender, about 3 hours.
Once the meat is very tender, remove from the pan and reduce the liquid by half until it has thickened to a glossy, sticky sauce.
Pick the venison meat into small pieces and add to a blender with the sauce and roasted bone marrow. Pulse to combine but still chunky in texture, not totally smooth.
Transfer the stuffing to a piping bag and pipe onto long sheets of pasta in 30 gram increments 2 cm apart.
Fold the sheet over and pinch to seal. Cut with a pasta wheel cutter and sprinkle with fine semolina.
Blanch the agnolotti in salted boiling water for 2-3 minutes.
Remove and toss with browned butter, sautéed squash and plate on top of the squash puree.
Garnish with the chives and parmesan cheese.