Grease a baking tray or oven dish, then preheat oven to gas Gas Mark 3: (325F) (160−170C).
Bring a large pot of salted water to a boil. When boiling, add dried spiral pasta and cook. Drain and drizzle with a little bit of olive oil to prevent mac from sticking.
Shred cheese and mix together then divide into three piles. Approximately 3 cups for the sauce, 1 1/2 cups for the inner layer, and 1 1/2 cups for the topping.
Melt butter in a large saucepan over medium heat. Sprinkle in flour and whisk to combine. Cook for approximately 1 minute, whisking often, and slowly pour in about 2 cups of the semi-skimmed milk whisking constantly until smooth. Slowly pour in the remaining semi-skimmed milk plus the whole milk whisking constantly until combined and smooth.
Continue to heat over medium heat, whisking very often until thickened to a very thick consistency.
Remove from the heat and stir in spices and 1 1/2 cups of the cheeses, stirring to melt and combine. Add and stir in another 1 1/2 cups of cheese, stir until completely melted and smooth.
Get a large mixing bowl, combine drained mac with cheese sauce, stir to combine fully. Pour half of the mac mixture into the prepared baking tray or dish. Top with 1 1/2 cups of shredded cheeses, then top that with the remaining mac mixture.
Sprinkle the top with the last 1 1/2 cups of cheese and bake for 15 minutes until cheese is bubbly and lightly golden brown.
Let rest 5–10 minutes before serving (it thickens up and scoops better). Garnish with parsley if desired
