Slice the beef into 4-5 even-sized pieces and trim off any large bits of fat. Season all over with salt and pepper.
Add a drizzle of oil to a large deep pot over high heat. Sear the beef until browned all over then remove and place in a bowl to one side. 5 or so mins should suffice - don't try and cook them through at this point, just caramelise the outside.
Lower the heat slightly to medium-high and add in the carrot, celery and onion. Fry until it all begins to soften and lightly colour, then add in the garlic and fry for a minute longer. Stir in the tomato puree and fry for a minute, then pour in the wine and use your wooden spoon to scrape off any flavour from the base of the pan.
Pour in the stock and passata, then add in the parmesan rind, bay leaves, thyme, rosemary, sugar and cooked beef (alongside all the resting juices). Give it a stir and bring to a simmer, then reduce the heat to low and pop on the lid.
Allow to gently bubble away for 1 hour 30 minutes with the lid on, then remove the lid and continue gently simmering for another 45-55 minutes, or until the sauce has thickened and the beef is tender enough to shred with two forks.
Remove the beef and place in a large baking dish, discarding the herbs and parmesan rind as when you find them. Roughly shred the beef then stir in back through the sauce. Check for seasoning, then add back to the baking dish and level off with a wooden spoon. Leave to sit as you make the bechamel sauce. Preheat the oven to 190C/375F.
Melt the butter in a medium-sized pot over medium heat. Stir in the flour to create a roux, then gradually add in the milk, whisking as you go to ensure no lumps form. Add in salt, pepper and nutmeg (can adjust later) then bring to a simmer. Allow to gently bubble away for 5 minutes until the sauce thickens, stirring regularly. Stir in 40g / 1/2 cup parmesan then check for seasoning and remove from the heat.
Layer over half of the ravioli on top of the ragu, then top a little under half of the bechamel sauce (if it has thickened a lot you can loosen it up with a splash of milk). Repeat, then finish with 30g / 1/3 cup parmesan to cover the top.
Bake in the oven for 20 minutes, or until golden/very lightly charred and bubbly around the edges. Leave to rest for 5 or so minutes before diving in!