Combine the base

• Place the egg yolk, mustard, lemon juice, vinegar and salt in a tall container or bowl.

Emulsify the oil

• Pour in the oil and blend with the immersion blender, keeping it at the bottom at first.
• Slowly lift the blender as the mayonnaise thickens and turns pale.

Adjust and store

• Taste and adjust the salt and lemon juice.
• Transfer to a jar and refrigerate.