Take a clean bowl and sit it on a damp cloth to avoid movement. Whisk two egg yolks at room temperature with a pinch of salt. Measure 250ml of light oil, either sunflower , olive or groundnut. Very slowly, whisking constantly, pour in a thin stream of the oil. Should the mixture split, add 2 tbsp of hot water and continue to whisk. Once the oil is incorporated, whisk in 1 tsp of Dijon mustard and 1 tbsp of white wine vinegar. Taste for seasoning. Add finely grated zest of 1 unwaxed lemon, 1 tsp of chopped capers, 1 tsp of chopped cornichons and chopped dill to serve with fish.