To make the Bouquet Garni, gather herbs in a small square of muslin and tie with kitchen string to secure.
Heat half of the oil in a large, ovenproof casserole dish over a medium-high heat and cook the beef cheeks in 2 batches for 8 minutes each batch, until browned all over and set aside.
Heat remaining oil in the dish over a medium heat and add onion, celery, carrot and leek and cook, stirring, for 5 minutes or until softened and lightly browned.
Return beef cheeks to dish with the stock, tomato, wine, lemon zest and bouquet garni and season with salt and pepper and bring to the boil.
Transfer dish to the oven and cook, covered for 2 hours.
Stir in eschallots and mushrooms and cook, uncovered for a further 40 minutes or until sauce has thickened and beef is very tender.
Remove from and reserve beef, eschallots and mushrooms; strain the sauce and discard vegetables and then return beef, eschallots and mushrooms to strained sauce.
Meanwhile cook potato in a large saucepan of boiling water over a medium heat for 15 minutes or until tender, drain and pass through a potato rice and then stir in milk and butter and season with salt and pepper.
Lightly spray a large frying pan with oil and heat over a medium heat and cook zucchini ribbons for 4 minutes or until just tender and season with salt and pepper.
TIP 1 - for a shortcut use a pre-prepared bouquet garni made with dry herbs.
TIP 2 - for a more intensely flavoured mash, try roasting instead of boiling the potatoes before mashing them.
TIP 3 - if you prefer a chunky sauce, omit straining the sauce, in step 8, so that you retain all the vegetables.