Place the butter, parsley, chilli flakes, garlic, lemon zest, salt, and pepper in a bowl and mix until well combined.

Take 2 tablespoons of the garlic butter and melt into a saucepan over medium heat.

Add the flour and stir for 1 minute or until mixture is sandy.

Add mustard powder and cheese and stir to combine.

Whisk in the milk and cook whisking for 3-4 minutes until slightly thickened and smooth, season with salt and pepper. This mixture should not be too thick you only want a light coating over the prawns.

Preheat oven grill to high.

Using a sharp knife, split prawns in half lengthwise. Wash and dry the heads. Place prawn halves, shell side down on to a baking sheet. Drizzle with oil and season with salt and pepper.

Pre-heat char grill or bbq over high heat, place prawns flesh side down on hottest part of grill and cook for 1-2 minutes or until slightly charred.

Remove prawns and place onto a baking tray, spoon over a little of the béchamel sauce and then some garlic parsley butter.