In a saucepan over medium heat, bring the water, sugar and corn syrup to a boil. Using a wet pastry brush, wash down any sugar crystals from the sides of the pan. Cook without stirring until the mixture turns golden.
Remove from the heat and add the cream gradually while stirring. Continue cooking over low heat, stirring constantly, until the mixture is smooth.
Whisk in the butter until the sauce is smooth. Let cool.
Preheat the oil in the deep fryer to 190°C (375°F). Line a baking sheet with paper towels or set a cooling rack on it.
In a large saucepan over medium-high heat, bring the milk to a boil with the butter and salt. Remove from the heat. Add the flour all at once and stir vigorously with a wooden spoon until the dough forms a smooth ball.
Return the saucepan to the burner over low heat and stir until the dough pulls away from the sides of the saucepan, about 2 minutes.
Remove from the heat and let cool for a few minutes. Add the eggs 1 at a time. After each addition, beat vigorously with a wooden spoon or electric mixer until the dough is smooth.
Using a pastry bag fitted with a 1/2-cm (1/4-inch) star tip, pipe 15-cm (6-inch) ribbons one at a time into the deep fryer. Fry about 8 crullers at a time, turning them halfway through cooking, until golden, 4 to 5 minutes. Drain on the baking sheet.
In a deep stainless steel mixing bowl, combine the sugar and cinnamon.
Dip the hot churros into the sugar mixture. Shake the bowl to coat well and shake off the excess sugar. Set churros aside on a baking sheet preheated to 100°C (212°F).
Repeat with the remaining dough.
Pile the crullers in 8 bowls, drizzle with sauce and sprinkle with marshmallow pieces. Serve warm.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.