Mix the flour and salt in a bowl. Pour in the milk, stir until smooth. Stir in the egg yolks. Pass the potatoes through a food mill into a bowl, mix in along with the butter. Beat the egg whites with the salt until stiff, carefully fold into the batter.
Heat a dash of oil in a non-stick frying pan. Fry the mushrooms for approx. 5 mins. per batch, remove, season. Reduce the heat, sauté the shallots and garlic in the same pan, add the tomato puree and porcini mushrooms, cook briefly. Pour in the wine and reduce almost completely. Return the mushrooms to the pan along with the thyme, pour in the stock and balsamic, bring to the boil, reduce the heat, simmer for approx. 10 mins.
Shredded potato pancakes
Preheat the oven to 60°C, warm the platter and plates. Heat a little clarified butter in a non-stick frying pan. Pour half of the pancake batter into the pan. Reduce the heat, cook for approx. 5 mins. until the underside separates from the pan, then turn the pancake and finish cooking. Tear into pieces using 2 spatulas, keep warm. Follow the same procedure with the remainder of the batter. Serve the shredded pancakes with the mushroom ragout.