How to Make the Cinnamon Scented Custard; In a medium saucepan combine the ¼ cup sugar and the 3 tablespoons cornstarch. Stir in the milk, egg yolks and lemon peel.
Cook and stir over medium heat until mixture thickens and just begins to bubble, around seven to eight minutes. When mixture thickens, it will coat a metal spoon when dipped into the egg mixture.
Do not boil. Remove from heat, remove cinnamon stick and add the first teaspoon of vanilla.
Pour into a bowl and place a piece of plastic film directly onto the custard to prevent skin from forming. Cool custard for at least 30 minutes.
How to Assemble the Panettone Trifle: In a 1 ½ quart serving bowl arrange slices of panettone (cut to fit the bowl) at bottom of serving bowl. Sprinkle with half of the amaretto. Spoon half of the custard on the panettone slices.
Sprinkle toasted almond slices over custard. Arrange slices of panettone (as needed) atop custard. Sprinkle remaining liquor over the panettone slices. Spoon remaining custard over the panettone slices.
Whip cream with the 2 tablespoons sugar and remaining teaspoon of vanilla to soft peaks. Spread the cream mixture atop the custard and using a pastry tube, pipe remaining cream around edge of bowl.
Chill for at least 4 hours. Sprinkle with remaining sliced toasted almonds.