Nutrition per serving may change if servings are adjusted.
3 cups low-fat milk
2 tablespoons light brown sugar
6 cinnamon sticks, broken into small pieces
1 vanilla bean, split in half lengthwise
2 large egg yolks
1/4 cup light corn syrup
2 tablespoons cornstarch
1/4 teaspoon ground cinnamon
2 cups marshmallow creme, such as Fluff
Combine milk, brown sugar, cinnamon sticks and vanilla bean in a large heavy saucepan. Heat over medium heat, stirring to dissolve the sugar, until steaming. Remove from the heat, cover the pan and let steep for 30 minutes. Strain, discarding the cinnamon sticks and vanilla bean halves. (Scrape the tiny seeds inside the vanilla bean into the milk, if desired.)
Whisk together egg yolks, corn syrup, cornstarch and ground cinnamon in a mixing bowl. Gradually add the milk, whisking to combine, and return to the saucepan. Cook over medium heat, whisking constantly, until the mixture boils and thickens, about 3 minutes. (Because the custard is thickened with cornstarch, it will not curdle when it boils.)
Transfer the custard to a bowl and place a piece of wax paper or plastic wrap directly over the surface to prevent a skin from forming. Cover and refrigerate until no longer warm. Add marshmallow creme and mix with a whisk until as smooth as possible. (The mixture will be slightly lumpy, but will smooth out during stir-freezing.) Return to the refrigerator until completely chilled.
Pour the custard mixture into the canister of an ice cream maker and freeze according to the manufacturer's directions. If necessary, place the ice cream in the freezer to firm up before serving in chilled dessert dishes.
Make Ahead Tip: Use within hours of freezing, if possible, or store in the freezer for up to 4 days. If the ice cream becomes very hard in the freezer, let it soften for 20 minutes before scooping.