Chill any remaining custard, and serve it with the remaining ladyfingers for dipping.
Sprinkle gelatin over 1/2 cup cold water; stir and let stand 5 minutes. Whisk together egg yolks and next 3 ingredients in a bowl.
Bring half-and-half to a simmer in a medium saucepan over medium heat. Whisk 1/4 cup hot half-and-half into egg mixture; add egg mixture to remaining hot half-and-half, whisking constantly. Reduce heat to medium-low, and cook, stirring constantly, 8 to 10 minutes or until mixture thickens and coats a spoon. Add vanilla, gelatin mixture, and 1/4 cup sherry, stirring until combined.
Remove from heat; let stand 15 minutes. Transfer to a bowl. Cover and chill 2 hours or until mixture is a pudding-like thickness, stirring every 30 minutes.
Arrange 23 ladyfingers in a single layer on a jelly-roll pan. Brush both sides of ladyfingers with remaining 1/4 cup sherry.
Line a 9-cup charlotte mold or soufflé dish with plastic wrap, allowing 2 to 3 inches to extend over sides. Line sides of mold with ladyfingers.
Beat cream at medium speed with a heavy-duty electric stand mixer 2 to 3 minutes or until soft peaks form. Fold whipped cream into chilled half-and-half mixture. Gently pour mixture into prepared charlotte mold. Cover and chill 8 to 24 hours or until fully set. To unmold, invert a flat plate over dessert. Holding containers together, invert. Lift off mold, and gently remove plastic wrap. Garnish as desired. Cut dessert into wedges.
Note: We tested with Natural Nectar Biscotti Savoiardi Lady Fingers.