Whisk together the single cream, eggs and cheese, season. Pour the sauce into the prepared dish.
Mix the parsnips with all the other ingredients up to and including the onions and 1½ tbsp of olive oil, season with salt. Mix the beetroot and remaining oil in a second bowl. Layer the vegetables alternately in the sauce. Place the rosemary in amongst the vegetables.
Approx. 1 hr. in the lower half of an oven preheated to 200°C. Remove and leave to stand for approx. 5 mins. Drizzle with the balsamic.