Preheat the oven to 220C/200 Fan/Gas 7 and butter a 23cm x 30cm x 6cm dish.
Heat oil in a large non-stick frying pan and brown mince all over.
Add onion and garlic, sprinkle in the flour and stir.
Stir in tomatoes, tomato puree and sugar, season, bring to a boil, cover and simmer for about an hour or until tender.
To make the creme fraiche sauce, measure the cornflour into a saucepan, add mustard and two tablespoons of creme fraiche, and whisk until smooth.
Add remaining creme fraiche and season, bring to the boil whisking until slightly thickened.
Layer the lasagne by dividing the meat sauce into three and spooning a third into the base of the dish.
Spoon a third of the creme fraiche sauce over the top, sprinkle with a third of the Parmesan.
Arrange a single layer of four sheets of pasta without overlapping.
Repeat using two more layers each of the mince sauce and creme fraiche sauce and one of the pasta, finishing with mince and creme fraiche sauce on top.
Sprinkle the remaining parmesan on top.
If planning to eat the same day, cook in the preheated oven for about 25 to 35 minutes or until the top is golden brown and the pasta is tender.
