Add <quantity>150<unit>g</unit></quantity> of unsalted butter to a saucepan over medium heat and melt

Cook the butter for 15m until it gets brown and nutty. Lightly shake the pan every once in a while to cook evenly

Remove from the heat. The brown butter is ready

Cover a saucepan with a kitchen towel and place a large heat-proof bowl on it

Separate <quantity>2</quantity> egg yolks and add them to the bowl

Add <quantity>1<unit>tbsp</unit></quantity> of vinegar and season with salt to taste

Add <quantity>1<unit>tsp</unit></quantity> of mustard and whisk to combine

Pour the warm Brown Butter into the bowl in a very thin stream while whisking

Pour <quantity>150<unit>ml</unit></quantity> of sunflower oil in a thin stream while whisking. Continue whisking until thick

Transfer to a bowl. The brown butter emulsion is ready

Coat the langoustine tails with vegetable oil

Place the tails onto a hot charcoal grill and cook for 1m on each side, until they turn white and opaque. Season with flaky salt to taste. The grilled langoustine tails are ready

Plate the tail and add <quantity>1<unit>tbsp</unit></quantity> of the Brown Butter Emulsion next to it. The grilled langoustine with brown butter emulsion is ready

Enjoy! This is an extremely simple yet delicious and elegant dish!