Heat the oil in a pan over medium heat.
Add the carrot, celery, onion, pepper, oregano and garlic and cook for about 6 minute, add a dash of water if the pan becomes dry.
Add in the tomatoes and 300 mills of water.
Simmer uncovered for about 15 minutes. Remove from the heat and puree the sauce until it is smooth.
Place the milk, butter, bay leaf and nutmeg in a small pan. Slowly heat the milk until the point at which it is about to boil.
Remove the bay leaf and sieve in the flour.
Use a whisk to blend the flour into the milk, do this until it begins the thicken.
Remove from the heat and add the egg and yoghurt and whisk until it is smooth. Spinkle in the cheddar and season to taste.
Pre-heat the oven to 180 degrees. You will need a large lasagne dish.
Add the mince and cook for about 10 minutes, until browned. Stir in the tomato sauce and basil.
Pour half the mince into the lasagne dish. Top with a layer of lasagne sheets.
Pour the rest of the mince and top with a second layer of lasagne sheets. Pour the cheese sauce on top.
Place the lasagne dish in the oven and cook for about 20 minutes, until golden and bubbling.
Leave the cooked lasagne to stand for five minutes. Divide between warmed serving plates.