Canola oil, for greasing
2 tablespoons unflavored powdered gelatin
2 cups sugar
2/3 cup plus 3 tablespoons light corn syrup
3 tablespoons honey
Lightly grease an 8-inch square cake pan with canola oil. In a medium heatproof bowl, mix the gelatin with 1/2 cup plus 2 tablespoons of cold water; let stand for 15 minutes. Set the bowl over a saucepan of simmering water and cook, stirring occasionally, until the gelatin dissolves and the mixture is smooth.
Meanwhile, in a medium saucepan, combine the sugar, corn syrup, honey and 1/3 cup plus 2 tablespoons of water and bring to a boil, stirring to dissolve the sugar. Cook the syrup over moderately high heat until it registers 250° on a candy thermometer. Immediately pour the hot syrup into the bowl of a stand mixer fitted with the whisk. Scrape in the gelatin mixture and beat at high speed until a smooth white foam forms, about 4 minutes.
Spread the marshmallow in the prepared pan and smooth the surface. Press a lightly greased sheet of parchment paper on the surface and let stand until set, 3 hours.
Run a sharp knife around the marshmallow. Very lightly dust a work surface with cornstarch and invert the cake pan onto it, tapping to release the marshmallow. Using a lightly greased sharp knife, cut the marshmallow into 1 1/2-inch pieces.
Add 1/2 teaspoon ground Vietnamese cinnamon during the last minute of beating the marshmallow;
lightly dust the cut marshmallows with a sifted mixture of 2/3 cup cornstarch, 1/3 cup confectioners' sugar and 1 teaspoon ground cinnamon