Place the bacon and mince in a large saucepan. Cook until the mince is browned. Remove from the pan and leave to one side.
Add 2 tbsp of oil to the pan and soften the onions on a medium heat without letting them colour. Put the meat back into the pan, pour in the wine and cook for 10 minutes or so, stirring every so often. Then add the tomatoes, bay leaf and some salt and pepper.
Cover the pan and leave to simmer, stirring occasionally, for about 1 hour. Then leave to cook uncovered for a further half an hour until the ragu has thickened.
While the ragu is cooking, pour boiling water onto the dried porcini and leave it to rehydrate for 20 minutes. Heat 2 tbsp of oil in a frying pan and soften the chestnut mushrooms, closed cup mushrooms and chanterelles. Add the sage, cook for 3-4 minutes more then leave to one side.
Drain the porcini, keeping the water to add to the ragu sauce, chop the porcini and place them with the rest of the mushrooms.
To make the béchamel, melt the butter in a clean saucepan and slowly add the flour to it. Cook until the flour mixture is a golden sandy colour and has formed a roux, stir continuously.
Heat the milk in a different saucepan until it is just below boiling point. Add a small amount at a time into the roux, whisking until smooth every time. When all the milk has been added bring the sauce to the boil and cook for about 5 minutes until the sauce has thickened. Season with salt and pepper, then add the mushrooms and set aside.
Preheat the oven to 180°C/350°F/Gas Mark 4.
To assemble the lasagne, cover the bottom of the baking dish with a layer of ragu, then add a layer of pasta sheets. Cover with a thin layer of mushroom béchamel, then another layer of pasta sheets, then another of ragu.
Add another thin layer of béchamel, then pasta sheets, then continue repeating these steps until the dish is filled. Add a thick pouring of béchamel to the final pasta sheet layer. Add grated parmesan cheese and bake for 30-40 minutes until golden and bubbling. Serve with a leafy green salad dressed with a zingy vinaigrette.