Black Forest Icebox Cake

Name: Black Forest Icebox Cake
Ingredients: 6 eggs, separated; ½ Cup granulated sugar, plus 3 tablespoons; 1 ½ Teaspoon pure vanilla extract; 1 Cup all-purpose flour; ½ Teaspoon salt; Confectioners sugar for dusting; 1 Cup granulated sugar; ¼ Cup cornstarch; ¾ Teaspoon salt; 2 ½ Cups whole milk; ¾ Cup heavy cream; 1 egg, lightly beaten; ¼ Cup kirsch, or to taste; 1 Tablespoon unsalted butter, at room temperature; 2 Teaspoons pure vanilla extract; 1 ½ Cup heavy cream; ¼ Cup confectioners sugar; ½ Teaspoon pure vanilla extract; 3 Tablespoons Dutch-process cocoa powder, sifted; A generous 2 cups cherry preserves, whisked vigorously to ease spreadability, if necessary; Cocoa powder (optional) and fresh cherries for decorating