Use this stock to make our Lobster Shepherd's Pies.
Fill a lobster pot or other large pot two-thirds full with water. Bring to a boil. Add lobsters headfirst. Cover, and cook until shells are bright red, 5 to 6 minutes. Remove from water. Using kitchen shears, clip the tips of the lobster claws, and let drain. Let stand until cool enough to handle.
Remove meat from lobsters, reserving shells. Refrigerate lobster meat, covered, until ready to use. Cut shells into large pieces.
Melt butter in a medium stockpot over high heat. Add leek, carrots, and celery. Cook, stirring often, for 2 minutes. Stir in Lillet; cook for 2 minutes more. Add reserved lobster shells, the water, parsley, bay leaf, salt, and peppercorns. Bring to a boil. Reduce heat, and let simmer for 30 minutes.
Strain through a fine sieve; discard solids. Let cool.
Stock can be refrigerated for up to 2 days or frozen for up to 1 month.