1. Stun the lobster by placing it in the freezer for 20 minutes. Meanwhile, fill a large pot with cold water. Add a generous pinch of coarse salt, peppercorns and the bouquet garni. Bring to a boil.
2. Lower the lobster into the boiling liquid and let it simmer for 12 minutes. Plunge the cooked lobster in ice water, drain it and remove the meat. Slice each claw in half and dice the rest of the meat.
3. Peel and de-seed the tomato (see Notes) and avocado. Dice them and the artichoke hearts into 1/2cm cubes. Add the diced lobster meat and shallots.
4. Mayonnaise: In a food processor, blend the boiled egg with mustard until smooth, then whisk in the fromage frais. Season with salt and pepper. Gently stir the mayonnaise into the lobster mixture and adjust the seasoning.
5. Vinaigrette: Whisk together all ingredients. Season with salt and pepper to taste.
6. To serve, arrange a few lettuce leaves on each plate. Pack the salad into a ramekin or ring mould, and quickly tip it onto the bed of lettuce. Drizzle with the seafood vinaigrette and top with half a claw.