Part Two:
For langoustines:
Separate the head from the tail and reserve the heads. Using kitchen shears, carefully cut the shell on the underside of the tail up to the last section before the "fins". You want to leave this on because it will protect the thinner part of the tail meat from over cooking. Discard the shell fragments and wrap and refrigerate the cleaned tails immediately.
For shellfish butter:
Preheat oven to 300�F. Put the heads in a roasting pan. Slowly roast at 300�F until dry (about 15 minutes). Add butter, let it melt until it has foamed, but before the milk solids begin to brown (noisette) and add water. Let cook for 2 hours at 200�F. Strain in a bowl, let it congeal in the refrigerator and separate the butter from the water. Discard the remaining water. Melt the butter and strain through cheese cloth. Yields about 3 oz.
For langoustine broth:
In a saut� pan over medium heat, slowly saut� the langoustine heads with the shellfish butter. Pour the chicken stock, cook slowly. Skim the surface of the broth. Let cook for about an hour. Strain the broth through cheesecloth. Yields about 1 1/2 cups.
For the Chardonnay reduction:
Cut the onions in quarters, dice the quince, and simmer slowly in a pot with 1 tablespoon of unsalted butter. The vegetables shouldn't take on any color. Add the grapefruit zest, vanilla seed and pepper. Pour the wine and the langoustine broth; reduce quickly on the stove. When the liquid has been halved, add the remaining butter. Continue until the sauce reaches a desired consistency (about 15 minutes). Add the chili and mint; let them infuse for a few minutes and strain the sauce. Reserve for final assembly of the dish.