Lasagna has four main components - a meat and tomato sauce (British Bolognese Sauce), a white sauce with a bit of cheese in it, based on a classic béchamel sauce, layers of pasta sheets, and a molten cheese topping.
To begin, peel and slice the onion and add it, the bay leaf and the cloves to the milk. Leave to infuse for at least half an hour.
To make the Bolognese sauce
Chop the onion into small chunks and soften them in oil over medium heat in a frying pan. Meanwhile chop up your canned tomatoes (unless you've got pre-chopped ones) and put them and the juice into a decent-sized pan. Add the basil and pepper to the tomatoes, and bring to a boil. Then turn down the heat to simmer. When the onions are soft and translucent, but not browned, tip them into the frying pan, add more oil to the frying pan and bring it up to high heat. Add the minced beef and break it up in the pan with a spatula. Keep the beef moving to get it browned all over. When done, add it to the tomato/onion mix. Add the pepper, basil and tomato puree and stir well. Reduce the heat to a simmer and cook for about half an hour, stirring occasionally.
When cooked, taste the sauce and add salt if necessary. If the sauce is too runny (it should be moist but not sitting in liquid), turn the heat on full and reduce the excess liquid. You can use this sauce straight away, but it does improve if you leave it overnight.
To make the béchamel / cheese sauce
In a small saucepan, melt the butter on medium heat and sift in the flour a bit at a time. Keep stirring until the flour is all absorbed (this is called a roux). Strain the infused milk into the roux. Discard the onion, bay leaf and cloves. Stir the milk into the roux and cook for a few minutes until it thickens. Add the nutmeg and mustard, stir well, and then add half of the cheese. Keep stirring until the cheese has melted, then remove the sauce from the heat.
Assemble the Lasagna
Preheat your oven to 200°C (392°F).
You'll need an ovenproof casserole dish or similar. I prefer my layers of pasta to fit snugly up to the sides of the dish, and this involves a bit of cutting to shape. You can't cut dried pasta without it shattering, so I soak the sheets in boiling water for five minutes to make them pliable.
You'll need enough sheets of pasta to create 3 layers in your dish. If your pasta is pre-cooked, you can use it after soaking and cutting. For uncooked dried pasta, follow the manufacturer's instructions.
Butter the insides and bottom of your dish. Spread a thin layer of the bolognese sauce on the bottom. Cover this with a layer of pasta sheets, cutting them as necessary to fit the dish, and trying not to overlap the sheets. Spread another layer of bolognese sauce, and then a layer of the white sauce. Cover this with a second layer of pasta, and cover that with the remaining bolognese sauce. Add the final layer of pasta, the remainder of the white sauce, and sprinkle the cheese evenly on top.
Bake the lasagna for about 30 minutes, until the cheese on top is golden and bubbling.
You need to let the lasagna rest for 20-30 minutes after baking to allow the sauces to firm up a little. Otherwise you end up with a mess of sauces, cheese and pasta dribbled all over your plate. Serve with a crisp green salad and any kind of wine you fancy.