1. Preheat oven to 375. Saute the onions, leeks, celery and carrots until soft.
2. Add Lamb, brown. Add flour to make a roux, stirring constantly
3. Add Tomatoes, Tomato puree, stock, Bay leaf, Rosemary and Thyme. Simmer covered for 30 minutes, Season with Worcestershire, salt and pepper to taste
4. Meanwhile make the topping. Boil Potatoes and Parsnips till soft. Drain and mash with Butter and Milk. Stir in Horseradish and season with salt and pepper.
5. Spoon the meat mixture into an oven proof dish. Top with potatoes, then breadcrumbs and cheese. Bake until golden brown, 20-25 minutes