Mix the heaped teaspoon of cornstarch with 2-3 tablespoons of cherry juice from the jar until smooth.
Heat the cherries in a saucepan over medium heat for 3-4 minutes. Stir in the cornstarch mixture until smooth. Remove from heat, stir in the amaretto or cherry liqueur, and let cool to room temperature for about 15-20 minutes.
In a bowl, whip the cream until stiff peaks form, about 3-4 minutes.
In another bowl, mix together the yogurt, sugar, and sour cream until combined. Gently fold in the whipped cream until no white streaks remain.
Layer the cherry mixture and cream mixture into transparent glass bowls, starting with the cherries on the bottom and finishing with the cream on top. Use a tablespoon to portion evenly. Top each serving with an Amarena cherry for garnish.