1.Preheat the oven to 160ºC. Drizzle the mushrooms with olive oil and season with sea salt and pepper. Roast for about 10 minutes, then slice.
2.To make the béchamel sauce; over a medium heat, melt the butter in a saucepan until bubbling. Add the flour and stir. Allow to cook for 1 minute. Gradually add the milk, stirring constantly until a smooth sauce is reached. Add the pecorino and mustard, and stir until totally combined.
3.Cook the pasta according to the packet instructions. In a large casserole dish, combine the pasta, béchamel, ham, ricotta and mushrooms. Sprinkle with the pecorino and bake for 30 minutes. Serve with bread and salad mix. Drizzle with the oil, lemon juice and mustard.