Have you tried Kohlrabi as a sub for roast potatoes? I parboil mine first as they take longer to cook inside. Then 3 types of green veg or 2 plus cauliflower mash? That plus my stuffing made with ground almonds instead of breadcrumbs and the juice from the roast instead of gravy - then the main course is fine. Followed by a low carb Xmas style cake for pud or chocolate mousse.
