Preheat the oven to 180°C.
Peel the potatoes then rinse. Clean the cepe mushrooms. Peel and finely chop the garlic and the shallot. Cut the cepes in to thin slices. Use a mandolin to thinly slice the potatoes.
Melt 20g of butter in a saucepan. Add the garlic and the potatoes. Once the potatoes are golden, add the thyme, milk and cream. Cook over a medium heat for 15 minutes, stirring frequently. In the meantime, heat a frying pan to hot and add a little olive oil. Add the cepes and a pinch of salt. Once coloured on both sides, remove from the heat and set aside.
Place stainless steel serving rings on an ovenproof tray. Start with a layer of potatoes in each serving ring then a layer of cepe mushrooms and finish with a second layer of potatoes. Transfer to the oven and cook for 20 minutes.
Cut the steaks in to 4 pieces. Pick the rosemary from the stems, leaving only the tips intact then prick the beef pieces with the rosemary leaves.
Heat a frying pan and add a drizzle of olive oil. Colour the beef skewers on all sides. Season with salt and pepper then remove from the pan. Lower the heat, add the shallot and a few rosemary stalks. Soften and then add the balsamic vinegar. Add the veal or lamb glaze and a glass of water. Allow to reduce then add a knob of butter to the sauce.
Transfer the potato gratins to large dinner plates and remove the serving rings. Add the beef skewers to the plates and served with the shallot and balsamic vinegar sauce.
«Feel free to replace the cepes mushrooms with other wild mushroom varieties.»