Fill a large pot of water and bring to the boil.
Preheat the oven to 200 degrees
While the water is heating up, finely dice the onions, chop the parsley, grate the zucchini, slice the mushrooms and grate the cheese.
Melt the butter in a large fry pan then add in the onion, stir until the onion is tender and translucent.
Once the water is at boiling point add a large pinch of salt, then add the pasta and cook until al dente.
Add the drained tuna to the butter and onion, stir and then add the zucchini and sliced mushrooms.
Stir in cream cheese, tomato paste, manrub and just bring the sauce to the boil (avoid over cooking it as it will dry out)
Remove from heat and stir through the strained pasta, ¾ of the parsley and cheese (leaving some to sprinkle on top.
Pop the pasta mixture into a large oiled baking dish, sprinkle with Man grind, breadcrumbs and remaining cheese.
Bake until browned and crispy on top.
Sprinkle with parsley and serve!