Wash the potatoes and beetroot, cook until tender.
Wash the carrots and add them to the potatoes too (but only cook until tender, not too soft).
If you have peas, fill them with water and cook until tender. If you have green beans, it's enough to just blanch them.
Peel the onion and leave it whole. (Prick it with a fork, and we'll use it to whisk our mayonnaise).
Separate the eggs and use the yolks for the mayonnaise.