Passion Fruit Marshmallows: Sift together the powdered sugar and cornstarch, and set aside in a small bowl. Lightly grease a 8-inch x 8-inch baking pan with baking spray. Generously dust the sides and bottom with sifted powdered sugar and corn starch mixture.
Place the passion fruit puree in a bowl of a stand mixer. Sprinkle the surface lightly with the powdered gelatin. Allow the gelatin to absorb slightly as you distribute it. This will allow the gelatin to bloom properly.
Place the water, granulated sugar, corn syrup, and salt in a small saucepan and stir over low heat, until the sugar has fully dissolved. Bring mixture to a boil, immediately stop stirring, and heat until a candy thermometer registers 240°F (115°C). Remove from the heat immediately and pour the hot sugar into the passion fruit-gelatin mixture, stirring until the gelatin has dissolved.
Using the whisk attachment, beat the mixture over high speed for 6 to 8 minutes, or until it has tripled in volume and is thick and pale in color.
Meanwhile, beat the egg white to stiff peaks in a separate bowl using a hand-held mixer, or by hand with a balloon whisk. Beat the stiff egg whites into the marshmallow base, and mix thoroughly. Pour the marshmallow into the prepared baking sheet, sift the cornstarch/powdered sugar mixture evenly on the top. Allow the marshmallows to set in the fridge, uncovered, for at least three to four hours, or overnight.
Once the marshmallows have set, invert the baking sheet onto a clean cutting board. Using a large knife, cut the marshmallows into 1-inch pieces and place in a large bowl, or on a large baking sheet. Dust with the remaining cornstarch/powdered sugar, and roll the marshmallows on all sides.
Store the marshmallows in an airtight container at room temperature for up to one week. Note: Slightly drier marshmallows will toast more easily than fresh ones.
S'more Assembly: Using a hand-held torch, toast marshmallows lightly, and sandwich them together with graham crackers and a square of bittersweet chocolate.
Tips for Success:
Slightly drier marshmallows will toast more easily than fresh ones!
If you do not have a hand-mixer for the egg white, feel free to whip it by hand using a balloon whisk. It will only take 4 to 5 minutes due to the small amount!
Passion fruit puree or juice can be found at some Whole Foods, other specialty stores, or online.