Tip the meat back into the pan and add the tinned tomatoes, purée, stock and oregano. Stir everything together, cover and simmer over a low heat, stirring occasionally, for 35 mins. Meanwhile cook the spaghetti following pack instructions, then towards the end of cooking, stir half the parmesan into the Bolognese. Put a spoonful of the pasta water into the sauce to loosen it, if it looks too thick, then drain the spaghetti. Tip the pasta onto the sauce, toss everything together to coat and season well. Garnish with the remaining parmesan and a few basil leaves.