Sauté onions and garlic in butter until soft. Add mince and herbs and cook for a few minutes, stirring to break up lumps. Add nutmeg, mushrooms, miso and wine; stir well. Bring to a simmer, cover and cook 40 minutes.
Remove lid and cook until most of the liquid has evaporated. Season to taste.
Meanwhile, boil pasta until al dente. Drain and run cold water over until cool.
Turn oven to 180°C/350°F/Cas Mark 4. Lay a sheet of pasta on a board (you may need to cut it in half) and spoon some mixture into the centre. Roll into a tube and place in a lightly oiled roasting dish, big enough to hold all tubes snugly in one layer.
Bring tomatoes, crème fraîche and cream barely to the boil in a small pan. Pour over pasta and sprinkle with parmesan. Bake until bubbling and golden.