This luminous gelled ring alludes to the canned cranberries of midcentury holiday tables. We've amplified the flavor with cherries.
Combine cranberries, cherries with juices, granulated sugar, vanilla bean and seeds, 1/4 teaspoon salt, 1 cup cherry juice, and 2 cups water in a large pot. Bring to a boil and cook until cranberries burst and mixture is slightly thickened, 10 to 15 minutes.
Strain mixture in batches through a fine-mesh sieve, gently stirring but not pressing on solids; discard solids. (You should have 4 cups liquid; add more water, if necessary.)
Return half of strained liquid to pot and bring to a simmer. Sprinkle gelatin over remaining 1 cup cherry juice in a bowl; let soften 2 minutes. Add a ladleful of hot liquid to gelatin mixture, then pour gelatin mixture into hot liquid in pot, stirring until gelatin is dissolved. Add rest of strained liquid; let cool completely. Pour mixture into a 4-to-6-cup mold lightly coated with cooking spray; refrigerate until set, at least 12 hours and up to 3 days.
Brush both sides of sage sprigs (including stems) with egg whites and sprinkle generously with sanding sugar. Let dry on a baking sheet lined with an oiled wire rack, at least 8 hours and up to 3 days.
Dip bottom of mold into warm water, 30 seconds, then run a thin knife around edge to loosen. Invert mold onto a platter, then lift to remove bowl. (If mold does not release, return to warm water 20 seconds more.) Serve, garnished with gooseberries and sugared sage sprigs.