Slice eight 1/4-inch slices of pound cake. Spread the Holiday Jam over 4 slices, top with remaining slices. Cut into 1/2" cubes. Set aside.
To make the custard, whisk together 3 tablespoons granulated sugar and cornstarch. Whisk in the egg yolks. Whisk in the milk and transfer to a medium saucepan. Stirring constantly, cook over medium heat until thickened, do not boil. Remove from heat, add vanilla and cool.
In each martini glass layer the pound cake cubes, then a layer of custard, repeat.
Beat whipping cream with confectioner’s sugar and vanilla until stiff peaks form. Top each trifle with whipped cream. Sprinkle with Amaretti cookie crumbs.