In a saucepan, over a medium heat, melt and whisk together the butter and cream cheese until fully combined and emulsified.

Continue to whisk, add the cream and bring to a gentle boil. Allow to gently blip, reduce and thicken until it coats the back of a spoon.

Add the egg yolk, continue to whisk and cook for 1–2 minutes.

Take off the heat, add the cheese and stir till fully melted and incorporated.

Season with salt and pepper and use as you would a béchamel, for carbonara, cauliflower cheese and lasagna.