Chicken Liver Mousse with Riesling-Thyme Gelée

For mousse:

Mellow the flavor of the chicken livers by placing them in a glass bowl with 2 cups milk. Cover; chill for 2 hours. Drain; discard milk. Return livers to same bowl, add the remaining 2 cups milk, cover, and chill for 2 more hours (or overnight). Drain; discard milk and rinse livers. Pat dry with paper towels.

Set a fine-mesh strainer over a medium bowl; set aside. Melt 2 tablespoons butter in a large skillet over medium-low heat. Add shallots and thyme and cook, stirring occasionally, until shallots are very soft, about 10 minutes. Add livers, increase heat to medium, and cook, turning once, until livers are firm but still pink inside, about 4 minutes. Remove pan from heat and stir in Calvados. Return to heat; cook until Calvados is reduced by half, about 30 seconds. Discard thyme.

Transfer liver mixture to a food processor; add 2 teaspoons salt and pepper. Process until smooth. With processor running, add remaining butter by tablespoonfuls until all butter is incorporated. Transfer mousse to prepared strainer. Using a rubber spatula, press mousse through strainer. Rinse and dry strainer, then strain mousse again, discarding solids in strainer. Divide among small jars. Chill until firm, 12 hours.

For gelée and toasts:

Place 1/4 cup water in a medium microwave-safe bowl. Sprinkle gelatin over water and let stand until softened, about 10 minutes. Microwave gelatin mixture until gelatin dissolves and mixture becomes clear, about 30 seconds. Add sugar; stir until dissolved. Stir in wine.

Spoon gelée over mousse in jars, forming a 1/4" layer (not all gelée may be used). Top each jar with thyme sprigs or leaves, if desired. Cover with plastic wrap and refrigerate until gelée is set, about 1 hour. DO AHEAD: Can be made 3 days ahead. Keep chilled.

Preheat oven to 450°F. Arrange bread triangles on a rimmed baking sheet. Brush with melted butter. Bake until golden brown, about 5 minutes. DO AHEAD: Can be made 1 day ahead. Store airtight at room temperature.

Let mousse soften slightly at room temperature for 30 minutes before serving with toasts.