RECIPE
(I believe it yielded ~350g of a marshmallow slab.)
Ingredients
100g egg yolks (~5-6 eggs)
2g salt
14g gelatin + 85g cold water (filtered, preferably)
180g sugar
60g water
~10g/2tsp vanilla extract of your preference
Directions
Bloom the gelatin in the cold water for 5-10 minutes. Add sugar and the other water quantity to a saucepan and heat on medium. Meanwhile, beat egg yolks and salt in the bowl of a stand mixer on low speed with a whisk attachment.
Heat sugar syrup to 240F/115.5C, turn mixer speed to high, and drizzle syrup into the side of the mixer bowl. Beat on high for several minutes, until mixture is cooled significantly and has increased in volume and is pale in color. In the same saucepan, gently melt bloomed gelatin, and add to the mixture, in addition to the vanilla. Beat for five minutes, then spread mixture into a greased loaf pan. Allow to dry for 8 hours minimum (preferably...16, I think).
Dust a cutting board with an equal mixture of corn starch and powdered sugar (25g each should be sufficient). Unmold marshmallow slab, dust the top, and cut into cubes. Toss cubes in remaining sugar/cornstarch mix.