Lobster Gelees with Fresh Tarragon Oil

Bring 6 quarts water to a boil in pot, then plunge 2 lobsters headfirst into water and cook, covered, 8 minutes from time they enter water. Transfer with tongs to a shallow baking pan to cool. Return water to a boil and cook remaining 2 lobsters in same manner.
When lobsters are cool enough to handle, remove meat from tail and claws and set aside. Cut tail shells and lobster bodies (not including claws) into 1-inch pieces with kitchen shears, then rinse well, discarding gills, eye sacs, tomalley, any roe, and claw shells. Transfer to a 6- to 8-quart heavy pot, then add wine, carrots, celery, fennel, onion, garlic, large tarragon sprigs, salt, fennel seeds, red-pepper flakes, and remaining 2 quarts water and bring to a boil. Reduce heat and simmer, uncovered, until liquid is reduced to about 6 cups, about 1 1/2 hours.
While stock reduces, scrape any coagulated white albumin from lobster meat with a knife and cut meat into 1/2-inch pieces, then chill, covered.
Pour stock through a dampened cheesecloth-lined large sieve into a large bowl, pressing on and then discarding solids. Transfer 2 3/4 cups stock to a bowl. (Cool remaining stock completely, uncovered, then freeze in an airtight container for another use.) Sprinkle gelatin evenly over 1/4 cup stock in a 1-quart saucepan, then let stand 1 minute to soften. Heat over moderately low heat, stirring, just until gelatin is dissolved, then stir in vinegar and remaining 2 1/2 cups stock.
Put molds in a baking pan. Add 2 teaspoons gelatin mixture to each mold and freeze until set, about 10 minutes. Put 1 small sprig of tarragon and a tip of claw meat in bottom of each mold, then divide lobster meat among molds. Fill with remaining gelatin mixture and chill, covered with plastic wrap, until set, at least 2 hours.
To unmold, dip 1 mold in a pan of hot water 3 to 5 seconds to loosen. Run a thin knife around edge of mold and invert gelée out onto a plate. Repeat with remaining molds. Drizzle plates with fresh tarragon oil .