Marie Rose sauce

Whisk together the egg yolk, mustard and lemon juice in a bowl

Very slowly drizzle the oil into the yolk mixture whilst whisking constantly. If the bowl is moving around too much while you do this, sit it on a few damp tea towels to hold it in place

Once the mayonnaise begins to thicken and emulsify, you can start adding the oil a little quicker. Season to taste with plenty of salt and pepper, then stir in the ketchup, paprika and cayenne. Serve sprinkled with a little more cayenne on top