Steam the lobsters in a large pot until they turn bright red and are cooked through, about 8-10 minutes. Remove and let cool slightly before handling.
Using a sharp knife, carefully crack open the lobster shells and extract the meat, keeping the chunks large and juicy. Avoid shredding into mush for the best texture.
In a mixing bowl, combine the lobster chunks with melted butter, mayonnaise, and freshly squeezed lemon juice. Gently fold to coat, being careful not to break up the meat.
Add the finely chopped celery and chopped herbs to the lobster mixture. Fold gently to evenly distribute the crunch and herbal brightness.
Toast the brioche buns lightly in a toaster or oven until golden brown and just crispy on the outside, keeping the insides soft.
Spread the lobster mixture generously into each toasted bun, filling them with a heaping scoop that stays firm and not soggy.
Squeeze a little extra lemon over the filled buns if desired, to brighten the flavors. Serve immediately to enjoy the perfect crunch and creamy filling.
