Add the garlic-infused oil to a 30cm oven-proof pan and place over a medium heat. Add the courgette and leek and allow to soften.
Add the mince to the pan too, break up and fry until browned. Add the chopped tomatoes, puree, stock, mixed herbs, salt and pepper. Mix until all combined.
Break the lasagna sheets into 2-4 pieces each and push them down into the sauce. Put them in all randomly, not on top of each other.
Allow to simmer until the lasagna sheets are cooked - as they become more flexible you can move them about a little. I like to have some bits more visible and some beneath the sauce.
A few minutes before the lasagna sheets are fully cooked, add dollops of mascarpone (or cream cheese), then swirl it around in the sauce a little. You don't need to full mix it in.
Sprinkle the grated cheese all over the top of the dish and then pop under a hot grill for 5 minutes or until the cheese is golden brown.