Firstly take the dried wild fungus and place into a bowl and pour over 150ml of boiling water. Set to one side.
Heat a heavy based pan with 2 tablespoons of sunflower oil and a knob of butter and set to a high. Seasoning the meat with salt and pepper, brown the venison in batches. Remove from the pan and set aside.
Now add the chopped onion to the unwashed pan: you want all the flavour from the venison, perhaps add a little more oil. Sauté until soft and translucent, add the chestnut mushrooms and sauté for a further 5 minutes. Add the flour, stir and cook for several minutes then add the tomato puree. Now add the beef stock in 3 additions, letting it come back to a simmer between each addition. Finally strain the liquor from the fungus through a fine sieve, (it can be gritty). Pour the liquor into the pan, the fungus will be added later. Add the cream, bay leaf, juniper berries and 1 sprig of thyme and simmer gently for 45-90 minutes or until the meat is tender.
Meanwhile, blanch the shallots in boiling water for 15 seconds. Drain and cool under running water, then peel. Pop the shallots into a frying pan, brown with a little oil and butter, then add to casserole 15 minutes before the end of cooking with the fungus.
Finally defrost the lingonberries, add the caster sugar and stir, leave to steep for an hour.
Serve with creamy mashed potato and the lingonberries with some fresh thyme.