Preheat oven to 200°C
Heat the oil in a large frying pan and sautÃ© the onion for about 5 minutes until softened. Add the garlic and cook for another minute. Turn the heat up and add the turkey mince, and fry until lightly browned. Pour in the wine and boil rapidly to allow the alcohol to evaporate and the wine to reduce a little. Add the can of tomatoes and tomato purÃ©e, sugar, basil and seasoning, stirring well. Turn down the heat to low and continue to cook for about 20 minutes until thick. Set aside.
To make the bÃ©chamel sauce, melt the butter and add the flour. Stir well with a wooden spoon and cook for two minutes. Pour in the milk a little at a time, whisking continuously until thickened. Add the bay leaf and simmer gently for about 10 minutes until you have creamy sauce. Discard the bay leaf.
To assemble the lasagne, spread a thin layer of meat sauce on the base of a gratin dish. Add a layer of lasagne sheets, avoiding any overlap and breaking them up if necessary to fit. Pour a layer of white sauce evenly on top, and a layer of meat sauce on top of this. Add another layer of pasta, followed by the last of the meat sauce and then finish with white sauce. Arrange the diced mozzarella on top and Parmesan and bake for about 40 minutes until cooked and golden brown.