Borscht Horseradish Terrine

PreparationMake horseradish cream layer: Lightly oil terrine. Cut a strip of parchment paper to fit in bottom of terrine and up the 2 ends, allowing overhang at each end. Put 2 teaspoons cold water in a small metal bowl, then sprinkle 1/2 teaspoon gelatin evenly over water. Let stand 1 minute to soften. Meanwhile, stir together sour cream, horseradish, 1/4 teaspoon salt, and 1/8 teaspoon pepper in a bowl. Heat softened gelatin in bowl set over a small saucepan of barely simmering water, stirring, until dissolved, about 30 seconds. Remove bowl from heat and stir in 2 tablespoons horseradish cream, then stir mixture into remaining horseradish cream until combined well. Spoon into terrine, smoothing surface, then chill until set, about 10 minutes. Make broth layer: Simmer broth, bay leaf, garlic, red-pepper flakes, cloves, and lemon juice in a 1-quart saucepan, covered, 5 minutes. Remove from heat and set aside. Put remaining 2 tablespoons cold water in cleaned small metal bowl, then sprinkle 2 teaspoons gelatin evenly over water. Let stand 1 minute to soften. Add softened gelatin to broth in saucepan and heat over low heat, stirring, until gelatin is dissolved. Strain broth through a fine-mesh sieve into a metal bowl, discarding solids. Transfer 1/2 cup broth to cleaned small metal bowl (reserve remaining broth in other bowl). Put small bowl (with 1/2 cup broth) into an ice bath and let stand, stirring gently, until broth is cool and syrupy. Spoon 1/4 cup cooled broth onto set horseradish cream layer (reserve remaining broth in small bowl at room temperature), then chill terrine until set, about 10 minutes. Make smoked-tongue layer: Add veal tongue and gherkin to larger quantity of reserved broth in bowl, then put bowl into a large ice bath and stir gently and constantly until mixture has consistency of raw egg whites. Pour mixture onto set broth layer in terrine and chill until set, 15 to 20 minutes. Make another broth layer: Spoon remaining 1/4 cup broth in small metal bowl over set tongue layer. (If broth has gelled, re-melt over barely simmering water, then put bowl into large ice bath and let stand, stirring, until cool and syrupy.) Chill terrine until broth layer is set, about 10 minutes. Make borscht layer: Stir together borscht liquid, 1/4 teaspoon salt, and 1/8 teaspoon pepper in cleaned 1-quart saucepan. Transfer 2 tablespoon seasoned borscht mixture to cleaned small metal bowl, then sprinkle remaining 2 teaspoons gelatin evenly over mixture. Let stand 1 minute to soften. Add softened gelatin to borscht mixture in saucepan and heat over low heat, stirring, until gelatin is dissolved. Transfer to cleaned small metal bowl. Put bowl in ice bath and stir gently and constantly until consistency of raw egg whites. Spoon over set broth layer and chill terrine at least 4 hours. To serve: Invert a large plate over terrine, then carefully invert terrine onto plate with aid of parchment. Cut terrine into 3/4-inch-thick slices. Cooks' notes:Terrine can be chilled (covered once set) up to 3 days