1. Place the milk, onion, close and bay leaf into a small saucepan over a medium heat. Bring to a gentle simmer for 1 minute, then remove from the heat and allow to stand and infuse for 15 minutes.
2. Strain the milk and discard the onion, clove and bay leaf. Return the milk to the saucepan and place over a high heat. Give the cornflour and milk mix a stir to combine, then add to the saucepan of infused milk, stirring constantly until the mixture is quite thick. Remove from the heat, add the cream, lemon juice and parsley, before tasting and salting as necessary. Allow to stand until ready to serve - the residual heat of the pan should keep the sauce warm (if not, give it a gentle blast of heat as you're dishing up).
250ml whole milk
1/2 white onion, peeled and cut into three
1 bay leaf
2 tsp cornflour mixed with 3 tbsp milk
75ml double cream
Juice of half a lemon
Big handful of flat-leaf parsley, finely chopped