Step 1

Put the vinegar in a small pan with the peppercorns and bay leaf. Reduce the vinegar over a high heat until there is only 1 tbsp left. Strain the peppercorns and the bay leaf from this reduction. Allow to cool.

Step 2

Whisk together two fresh egg yolks with the white wine vinegar in a large heat-proof bowl. Place the bowl over a saucepan of simmering water (do not to let the bowl touch the water) and whisk until lukewarm.

Step 3

Add the melted butter to the egg yolks very, very slowly, beating continuously. Once the mixture has thickened, remove from the heat and season with salt and pepper.

Step 4

Season to taste with salt and pepper and a little lemon juice.