Preheat the oven to 200C/ 400F. Pan-fry the sausages over medium-high heat until browned on all sides. Remove from heat and transfer to a plate.
Finely dice the onion. Melt the butter in the frying pan then sauté the onions until translucent. Add the thyme sprigs, bay leaf and add a good pinch of erythritol and saute for another minute.
Place the sauteed onions on a small baking tray and position the sausages and any juices on top. Roast in the oven for 15-20 minutes or until cooked through. The onions will caramelise but watch out they don’t burn as this will ruin the taste of the gravy.
While the sausages are roasting, make the cauliflower mash. Wash and trim the cauliflower then cut into small florets. Place into a glass bowl. Then drizzle 2 tablespoons of cream and 2 tablespoons of butter. Cover and microwave on high for 5 minutes, stir the cauliflower to coat with the cream mixture. Cover and microwave for another 3 minutes until soft.
Grate the cheese and set it aside. Carefully remove the cauliflower from the microwave and place it into a food processor or a high-speed blender along with the grated cheese. Pulse until a smooth puree, or mash by hand, then season with salt and pepper and a teaspoon of mustard.
When the sausages are cooked and the onions are caramelised, remove them from the oven. Turn the oven off and place the sausages onto a plate or tray, returning to the oven to keep warm.
Put the frying pan back on the stove and scrape in the caramelised onions. Add the vinegar, red wine, and stock cube and simmer for a few minutes until a thick sticky gravy forms. If it’s a little too thick, add a little water one tablespoon at a time to get to a pouring consistency. You can remove the thyme and bay leaf at this point or keep it in.
Remove the sausages from the oven. Spoon the mash onto the middle of the plate. Top with the sausages and pour over the gravy. Serve hot.