Eggs in Aspic with Sorrel Mousse

Whatever the garnish, the quality of eggs in aspic depends absolutely on the quality of the jelly. And, however sapid the jelly, all of its delicacy depends on the precise degree of natural gelatin contained in it: The jelly must be only just firm enough to hold its form easily, once unmolded—and it should tremble. No matter how rich and pure the flavor, an excess of gelatin will produce a rubbery and distinctly unpleasant material. A trembling jelly melts luxuriously on the tongue; a rubbe