In a large pot of boiling water, add the pasta and quartered cauliflower and cook for approximately 8 minutes (note: don’t worry if the pasta is not completely cooked as it will have more time to cook in the oven).
While the pasta is cooking, add the butter to a saucepan over medium heat and stir until completely melted. Mix in the flour and cook , stirring for 2 minutes. Gradually add in the milk, continuing to stir until all the milk has been added in and the sauce has started to thicken. Add in 1 cup of cheese and stir until the cheese has melted. Remove from heat.
In a bowl, add the breadcrumbs, 1 cup of cheese and parsley and toss to combine.
Once the pasta and cauliflower are cooked, drain and add them to the baking dish. Use a fork to break up the cauliflower into small chunks. Mix in the tuna and the white sauce.
Top the pasta with the breadcrumb mixture and place in oven for about 10 -15 minutes or until golden.
