Serve with raw oysters and clams on the half shell.
Heat vinegars and 1/2 cup water in a small saucepan over medium heat until warm. Remove from heat; add gelatin, and stir until dissolved. Transfer to a nonreactive medium bowl. Stir in salt, pepper, lemon juice, and shallots. Cover, and refrigerate, stirring occasionally, until mixture has jelled, at least 6 hours (or overnight).