1.For the mussels, heat oil in a large pot until hot then toss in the onion and garlic, lower heat and simmer for 5 minutes. Add thyme, wine and mussels. Bring to the boil, place lid on the pot and simmer for 8–10 minutes, or until the mussels open (discard any that don’t open). Strain and reserve liquid.
2.Place potatoes in a large pot of cold water and bring to the boil. Simmer for 15 minutes or so, until tender, then drain. Leave for 3-4 minutes to allow steam to escape while you work on the next step, then transfer to large bowl. Ladle ½ cup mussel liquid onto potatoes, so they absorb the flavour, then set aside.
3.Place carrot, peas, peppers, onion, tomatoes, eggs and gherkins in a bowl. Add garlic mayonnaise. Take mussels out of shells and add to salad. Mix well.
4.To serve, place potatoes on a serving plate, spoon salad on top and garnish with chopped chives.