Lemon Mayonnaise

Add the egg yolks, lemon juice, mustard powder and lemon zest to a blender. Blend at the lowest speed for 20 seconds or so.

Very slowly pour in the olive oil with the blender at low speed. After ¾ of the oil has been added, check for flavour and texture. Add further oil until you are happy with the taste etc.

Season carefully with salt and more lemon juice (if required)