1. Heat oil in a heavy based pan, gently sauté the onions until just soft, raise heat and add meat in batches, brown on all sides and remove from pan to do remainder.
2. Add diced beetroot to the pan and return all meat, stir in three quarters of the stock, bring to the boil and then simmer, stirring occasionally, for 45 minutes or until beef and beetroot are tender. You may have to add more stock during the cooking process.
3. Meanwhile, slice the baguette into thick slices, brush with oil and toast under a hot grill on both sides. Crumble half the cheese onto the croûtes.
4. Once the meat is cooked, stir in the remaining cheese – broken into crumbles so it melts easily, and the horseradish.
5. Pop the croûtes back under the hot grill to just melt cheese and serve on top of the casserole.