Coat a large baking sheet with an even layer of cornstarch or powdered sugar (I use about 2 cups, but it can vary based on the size of your pan). Use the back of a spoon to make 24 indentations that are about 1 inch apart in the cornstarch or powdered sugar. This will be where you pipe each frog marshmallow. Set aside.
In the small bowl, add 2 Tbsp cold water and sprinkle 1 1/2 tsp of powdered gelatin evenly over the surface. Set aside to bloom.
In a large bowl, beat 2 large egg whites (70g) on a medium-high speed until they look foamy and reach the soft peak stage. Then, gradually mix in 3 Tbsp granulated sugar (35g) at a medium-high speed for about a minute, or until the mixture looks fluffy and has soft to medium peaks.
In a medium saucepan, combine the remaining 1/3 cup granulated sugar (65g), 1 Tbsp corn syrup (20g), and 1 Tbsp + 1 tsp water (20g). Cook over medium-high heat, stirring with a rubber spatula until the sugar dissolves and the mixture comes to a boil. Remove from heat.
With your mixer on low speed, slowly pour the hot syrup into the egg-white mixture in a steady stream. Gradually increase to high speed and whip until the marshmallow becomes thick, fluffy, and glossy (it usually takes me about a minute).
Heat the bloomed gelatin from step 1 in the microwave for 10-15 seconds, or until it just becomes fluid. You don't want to overheat the gelatin, or it can prevent your marshmallows from setting properly. With your mixer on low speed, pour the warm gelatin into the egg-white mixture and mix until the gelatin is just incorporated. Scrape the sides and bottom of the bowl with a rubber spatula to make sure it's properly combined.
Then fold 1 Tbsp vanilla extract and a pinch of fine salt into the mixture with a rubber spatula.
Scoop about 1/2 cup of the uncolored marshmallow mixture into a small piping bag and seal the top of the bag with a rubber band. Set aside.
Scoop about 1/4 cup of the uncolored marshmallow mixture into a small bowl and use a rubber spatula to mix in a generous squirt of black gel food coloring. Gently stir the mixture until it's evenly colored. Scoop the black marshmallow mixture into a small piping bag and seal the top of the bag with a rubber band. Set aside.
Color the remaining marshmallow mixture a warm green using equal amounts of green and yellow gel food coloring. Scoop it into a large piping bag and seal the top of the bag with a rubber band. Set aside.
Cut a 1/2 cm opening in the bottom of the green marshmallow piping bag, and cut a super small, 2mm opening at the base of the white and black marshmallow mixture.
Then pipe the marshmallow frogs on the prepared baking sheet, following the pictures above. Use the green marshmallow mixture to pipe an oval in each spoon indentation to be the frog's head (mine were about 1 1/4 inches wide), then add two green circles to the sides of the head to be the eyes.
Next, use the white marshmallow mixture to pipe a circle on top of the green marshmallow eyes, then use the black marshmallow to pipe pupils on top of the white marshmallow and add a smile. The marshmallows will set quickly, so I like to pipe a few at a time to make the eyes and smile look right. Note: The marshmallow in the piping bags will start to set as they sit and cool, so if you're having trouble piping or the marshmallows aren't smooth when you pipe them, heat the bag in the microwave for 2-5 seconds (it softens SUPER fast, do this in tiny, 2-second intervals!!)
Let the marshmallows sit at room temperature for a couple of hours or until they're firm. Once they're set, dust them lightly with cornstarch or powdered sugar to prevent sticking, then gently brush them off with a
fan brush or very soft brush and enjoy.