Cook the barley and parsnips in boiling salted water for approx. 35 mins., drain, retain approx. 100 ml of the cooking water, set aside.
Mix the linseed with the reserved cooking water, leave to absorb for approx. 30 mins.
Heat the oil in a non-stick frying pan. Stir fry the mushrooms and parsnips for approx. 5 mins., stirring occasionally. Reduce the heat, add the shallot and garlic, cook until the liquid has completely evaporated.
Mix the barley, linseed and vegetables with the nuts and all the other ingredients up to and including the pepper. Knead the mixture by hand until the ingredients form a compact mass, transfer to the prepared tin.
Approx. 35 mins. in the lower half of an oven preheated to 200°C. Remove from the oven, allow to cool slightly, turn out onto a plate.
Heat the oil in a frying pan. Stir fry the mushrooms for approx. 5 mins., season, set aside. Heat the oil in the same pan, fry the sage leaves until crispy, drain on a piece of kitchen paper, scatter the sage leaves and mushrooms on top of the barley & mushroom wreath.
Heat the oil in a pan, sauté the shallot for approx. 5 mins. Pour in the wine and reduce almost completely. Pour in the cream, reduce for approx. 5 mins., then puree. Add the lemon zest, season. Serve the sauce with the dish.