Line a lightly oiled 23 x 13-cm (9 x 5-inch) loaf pan with plastic wrap.
In a saucepan, off the heat, combine the sugar, flour, and cornstarch. Add the egg and whisk until smooth.
Gradually whisk in the hot milk. Bring to a boil over medium heat, whisking constantly and being careful to scrape the bottom and corners of the pan. Simmer for 1 to 2 minutes over low heat. Remove from the heat and add the butter, vanilla, and cinnamon. Stir until the butter has melted. Pour into the prepared pan. To avoid a skin to form on the surface of the custard, place a plastic wrap directly on the hot cream. Let cool. Refrigerate for about 6 hours or overnight.
Place the flour in a shallow bowl, the egg whites and water in a second bowl, and the breadcrumbs in a third.
Unmould the custard. Remove the plastic wrap and cut into 8 squares.
Gently dredge each square in the flour and soak in the egg mixture. Drain to remove any excess, then coat with the breadcrumbs, pressing lightly. Place on a plate and refrigerate for about 30 minutes (to firm up).
Line a baking sheet with paper towels or cover with a wire rack. Set aside.
In a large skillet, heat 1-cm (1/2-inch) of oil. Fry the custard squares in the oil on each side until golden brown.
Drain on the baking sheet. Sprinkle with the sugar.
If desired, garnish with a mini scoop of vanilla ice cream and drizzle lightly with a fruit sauce.
You can freeze the dessert after cooking. You just have to thaw in the oven at 170 °C (325 °F) for 15 minutes.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.