Preheat the oven to 200'C.
Peel the potatoes and then thinly slice on a mandolin. Peel and finely slice the onions.
Heat a large frying pan and then add the olive oil. Add the onions to the pan along with 3 or 4 sprigs of thyme. Sauté for 3 minutes, stirring every once in a while. Add the balsamic vinegar to the pan and continue cooking until all the liquid has evaporated. Mix the onions with the sliced potatoes.
Line the base of a large ovenproof dish with the potatoes and onions. Season with salt and pepper and then sprinkle over a few thyme leaves.
Bring the stock to the boil and then ladle it over the potatoes. Transfer to the oven and bake uncovered for approximately 45 minutes - check if the potatoes are cooked through using the tip of a sharp knife.
While the potatoes are cooking, prepare the rest of the dish.
For the steaks: heat a frying pan until hot and add a little sunflower oil. Season the steaks with Maldon sea salt.
Colour both sides of the fillets and then remove them from the pan. Reserve the pan. Transfer to a baking tray and cook for 5 to 10 minutes in the oven depending on the thickness of the steaks. When the steaks are cooked to the right degree, remove from the oven and allow them to rest for atleast 5 minutes.
Add the red wine to the steak pan and stir over a high heat to 'deglaze' the pan. Bring to the boil, reduce the heat and reduce to 100ml.
Add the chicken stock and bring back to the boil. Whisk the veal glaze in and reduec to the desired consistancy.
For the carrots: Trim off the leaves and the stalks. Peel the carrots if necessary. Pick the leaves from the tarragon and roughly chop.
Bring a pan of water to the boil and add a generous amount of salt.
Cook the carrots for 10 minutes in the rapidly boiling water and then drain. Season with salt, sprinkle over the sugar return to the pan with the butter. Cook over a medium heat until the carrots are glazed with the butter and sugar and then add the chopped tarragon.
Peel and grate the horseradish, softly whip the double cream,fold in the salt and pepper and grated horseradish.
Pick nice sprigs of watercress and keep fresh in cold water until ready to plate.
Place the steak on a plate with a small neat bundle of carrots on one side, and a dry sprig of watercress beside.
Serve the boulangere potatoes in the roasting tray or in a side dish on the table.
Spoon a quenelle of cream on top of the steak and either a small sauce jug of jus, or spoon some of the sauce around the plate.
« Fillet steak, while tender actually has less flavor than the more humble rump.Try the same dish with one of the 'cheaper' cuts to bring out its best. »