Put the butter and oil in a large heavy bottomed pan and heat over medium heat until the butter has almost melted.
Add the onions and sauté for 10 minutes.
Add the garlic, celery and carrots and cook for further 5 minutes or until the carrots and celery have softened.
Add the minced lamb to the pan, breaking up the meat with a wooden spoon and stirring until all the meat has browned.
Season with sea salt and black pepper
Add the wine and cook until it has mostly reduced.
Add the milk, and cook until it has mostly reduced.
Add the tinned tomatoes, bay leaves and thyme.
Cook for on a low heat until the lamb has become very tender (about 2 hours) gently stirring every 20 minutes. Do not let it boil - the heat should be just low enough to allow very gentle bubbles to rise to the surface.
Spinach Pasta
*You can mix by hand, but I always use a processor to mix the dough as it's easier and quicker.
Add the flour to the food processor, then add the other ingredients. Then pulse then ingredients until the ingredients form a consistent crumble, almost like breadcrumbs.
Tip the ingredients into a large bowl and using your hands, bring everything together into a smooth dough.
Wrap in clingfilm and allow to rest for 30 minutes.
Cut the dough in half, and flatten out by hand, and using a pasta machine, roll out pasta sheets to your preferred thickness.
Cut the pasta sheets so that they fit your baking dish
Bechamel Sauce
Melt the butter in a pan then add the flour. Mix quickly until a paste forms.
Cook for a minute or two on a low heat, stirring constantly to make sure the roux doesn't stick or burn.
Add a little milk, then whisk continuously until the milk is absorbed. Repeat until half of the milk has been whisked into the mixture.
Add the remaining half of the milk, whisking continuously to avoid lumps.
Cook the sauce on a gentle heat for 4-5 minutes. It's important to stir the sauce regularly, ideally with a whisk to stop the sauce catching or burning.
Assembly
Pre-heat the oven to 180°C.
Add a layer of the ragu on the base of the baking dish.
Then add a layer of spinach lasagne sheets, followed by a layer of béchamel sauce.
Repeat until you have used up all the ragu, pasta and béchamel sauce, or until you have filled your baking dish, making sure you finish with a layer of spinach lasagne.
Add a generous layer of grated parmesan cheese, season with ground black pepper then put the baking dish in the oven for 40-45 minutes. The lasagne is ready when the parmesan has melted and browned evenly.