Preheat oven to 180°C/350°F/gas mark 4. Grease and line a 500g loaf tin.
Melt the butter in a large pan and sauté the onion, without browning, celery and cook uncovered for 10 minutes.
Remove from the heat and add the pine nuts, parsley, lemon juice and eggs. Season well with salt, pepper and nutmeg, if using. Pour into the tin and bake for 40 minutes, until golden brown and fi rm in the centre.
To prepare the sauce, firstly place the mushrooms and water in a saucepan, bring to the boil then remove from heat and leave to soak for 40 minutes. Then drain, reserving the liquid, and chop the mushrooms.
Melt the butter in a saucepan, add the onion and fry for 10 minutes, until lightly browned. Add the mushrooms and gently cook for 3 minutes, until tender.
Mix the cornflour with the reserved liquid, Madeira and soy, then add to the mushroom mixture. Bring to the boil, stirring until slightly thickened. Season to taste.
Turn the roast out onto a plate, slice thickly and drizzle with the mushroom sauce.