Preheat oven to 220°C / 430°F (200°C fan).

Toss cauliflower in oil, salt and pepper. Spread on a large tray.

Roast 20 minutes (don't turn). Cauliflower should still be a bit firm, but with some colour on them. Remove from oven.

Turn oven down to 180°C/350°F.

Heat milk and cream until hot – either on the stove or in microwave.

Melt butter in a large saucepan or small pot over medium heat. Add flour and cook, stirring regularly, for 3 minutes.

While stirring, pour in half the milk. Once the roux is dissolved into the milk (mixture will thicken), stir in remaining milk. Stir on the heat for 1 minute – mixture should be thick enough to coat a wooden spoon.

Turn the stove off, but leave the pot on the turned off stove. Stir in salt, nutmeg and both cheeses. The cheese will thicken the mixture so it's like a thick sauce.

Add cauliflower and toss to coat in the sauce.

Transfer mixture to a 2L / 2qt baking dish (30 x 20 x 5cm / 12 x 8 x 2').

Sprinkle over gruyère followed by Red Leicester cheese.

Bake at 180°C/350°F for 30 minutes until the cheese is melted, and cauliflower is bubbly and golden.

Sprinkle with parsley if desired. Stand 5 minutes then serve!