Place all ingredients in the jug of your immersion blender (or a protein shaker if you don't have a jug).
Place blender at the bottom of the jug. Press the start button and don't let go while you move the blender up slowly. You will see the mayonnaise emulsifying (i.e. the mix becoming white and thick) as you go.
Stop blending once all the elements are fully combined.
Store in a glass jar in the fridge. It should keep for 7-10 days.