Preheat your oven to 200°C/400°F.
In heavily salted boiling water, add the cauliflower florets. Boil for 5-6 minutes, then drain and set aside.
In the same pan, add the whole milk, cheeses (reserve 50g of the red leicester), cayenne pepper, garlic granules, dijon mustard, salt, and pepper. Cook over low to medium heat.
While the cheese melts, prepare the cornflour slurry by mixing the cornflour with cold water until smooth.Stir in the cornflour slurry. Continue cooking until the sauce thickens.
Distribute the cauliflower across a baking dish, then pour the cheese sauce on top. Stir to combine, and top with the reserved red leicester. Pop in the oven for 20 minutes or until the cheese is golden and bubbly.
Leave to stand for 5 minutes. Garnish with freshly chopped parsley before serving. Dig in!