2 egg yolks (at room temperature)
2tsp white wine vinegar
1tsp English mustard
2tsp Dijon mustard
Freshly ground white pepper
100ml olive oil mixed with 200ml vegetable oil
Juice of half a lemon (optional)
Put the egg yolks, white wine vinegar, mustards and salt and pepper into a stainless steel or glass bowl on a damp cloth to stop it slipping (don't use an aluminium bowl, otherwise it will make the mayonnaise go grey).
Mix well with a whisk, then gradually trickle the oils into the bowl, whisking continuously. If the mayonnaise is starting to become too thick, add a few drops of water and continue whisking in the oil. When the oil is all incorporated, taste and re-season if necessary and add a little lemon juice.