Pour 1/3 cup of cold water into the bowl of an electric mixer and sprinkle the powdered gelatin on top. Let sit for 5 minutes.

Place the sugar and ¼ cup cold water in a small pot and set to medium-high heat. Stir until the sugar has melted.

Attach a candy thermometer to the pot and boil the sugar until it reaches 238F. Brush the sides of the pot with a wet pastry brush if sugar crystals stick to the sides.

Add the hot sugar to the gelatin and stir the mixture by hand whisking for a few minutes to slightly cool. Then beat with an electric mixer on medium-high speed for 8-10 minutes, until soft peaks form. Then add the vanilla bean seeds and mix well.

Place 2/3 of the marshmallow in a piping bag fitted with a round tip, and divide the remaining marshmallow in half, dyeing half black and half yellow.

Thinly spread the yellow and black marshmallows on a baking sheet lined with parchment paper. Pipe the white marshmallow into oval rice ball shapes on another baking sheet lined with parchment paper. Set both baking sheets aside.

Make the marshmallows following steps 1-4 above.

Divide the marshmallow into 3 bowls and dye it red, pink and orange. Place half of the red and pink marshmallows into piping bags fitted with small round tips. Place half of the orange marshmallows into a piping bag fitted with a flat tip.

Thinly spread the remaining red, pink and orange marshmallows onto a baking sheet lined with parchment paper. Dot the orange marshmallow with any residual white marshmallow stuck to the whisk attachment. Use the red marshmallow in the piping bag to create the ikura (fish eggs) and the ebi (shrimp). Use the pink marshmallow in the piping bag to fill in the details of the shrimp. Use the orange marshmallow in the piping bag to create the uni (sea urchin). Set aside for about 1-2 hours, for the marshmallows to stiffen.

Dust the trays with the coloured marshmallows in a layer of corn starch. Slice the red (tuna), pink (fatty tuna), orange (salmon) and yellow (egg) into rectangles that are slightly larger than the marshmallow rice. Gently peel these off the parchment paper and stick them onto the marshmallow rice, pressing down to adhere them. Repeat with the ikura (fish eggs), ebi (shrimp) and uni (sea urchin).

Slice the black (nori seaweed) marshmallow into strips and wrap them around the egg, fish egg and sea urchin sushi. If you’re lacking space, remove the fish egg and sea urchin sushi from the tray before wrapping the nori marshmallow around them. (Note: If the marshmallows are too sticky, dust the sticky areas with corn starch, but make sure to keep the areas in between each marshmallow piece sticky. The stickiness acts like a glue to stick the different pieces together.)

Cover the sushi in another layer of cornstarch, then gently peel them off the parchment paper, flip upside down, and coat in another layer of cornstarch. Bounce the sushi in a mesh sieve to remove any excess corn starch. To store, place the marshmallows in one layer in a Ziploc bag. These will stay fresh for about 3-5 days.