Add 1 turn of the pan EVOO to the pot and heat until it begins to smoke. Add meat and caramelize until deep brown. Remove to a plate and add remaining tablespoon oil, another turn of the pan. Add bay, vegetables and garlic, and reduce heat to medium. Cook 12-15 minutes, until tender, then sprinkle in flour. Cook a minute then stir in tomato paste and Worcestershire. Deglaze the pot with wine or beer and stir in stock. Reduce heat and let simmer to thicken and combine flavors. When ready to assemble casserole, wilt in ‘cress and remove bay.
Drain and mash potatoes and parsnips with milk and butter or sour cream. Melt in cheese and season potatoes and parsnip mash with salt, pepper and nutmeg to taste.
Place meat and mushrooms in a large casserole dish and top with the potatoes. Bake 20 minutes or until brown.
For a make-ahead meal, let assembled casserole cool completely then refrigerate for up to 4 nights. Bake covered for 45 minutes at 375°F and 20-30 minutes longer uncovered, until brown.
To freeze, let assembled casserole cool, then wrap in plastic then foil. Defrost casserole one day ahead and cook for 1 hour at 375°F covered with foil, then 20-30 minutes more uncovered, until brown.