1 lobster tail in its shell
1 red Asian shallot
1/2 bunch watercress
125 g kewpie mayonnaise
2 tsp lemon juice
1 tsp white wine vinegar
1 tsp mustard powder
60 ml olive oil
4 brioche buns
40 g butter, softened
Bring a large saucepan of water to the boil over high heat, then reduce the heat to medium until the water is at a constant simmer.
Poach the lobster tail in its shell in the simmering water for about 8–10 minutes, remove the lobster from the pan and set aside to cool. Place in the refrigerator until chilled.
Shell the lobster and slice the meat into 8 discs, finely chop any small or discoloured pieces of lobster you may have.
Cut the shallot in half length ways and thinly slice each half.
Pick the watercress, discarding any bruised or tarnished leaves, then wash and pat dry.
Combine the kewpie mayonnaise, lemon juice, vinegar and mustard powder in a mixing bowl. Slowly add the oil while whisking continuously, season to taste.
Preheat the oven to 180°C (350°F).
Cut the brioche buns in half horizontally and lightly butter them, put the buns on a tray, butter side down, and toast them in the oven for 5 minutes or until golden brown.
Spread 1 teaspoon of the mayonnaise onto each half of the brioche, place a tablespoon of chopped lobster on the bottom halves and season to taste, arrange 2 discs of lobster meat on top without overlapping.
Place 1/2 teaspoon mayonnaise on each lobster slice and season again to taste, add a few slices of shallot and a few leaves of watercress, place the brioche lid on the top and serve immediately.