First of all, put the isinglass to soak in cold water (85 g) and let it rest like this.

Meanwhile, pour water (80 g), sugar and glucose into a saucepan to prepare the syrup: if you have a kitchen thermometer, you will need to reach a temperature of 115-120 ° C; if you don't have a thermometer for sweets, bring to a boil and let it boil for a few minutes, dip a fork in the syrup and blow gently through the prongs: the syrup will be ready when it swells like a soap bubble.

In the meantime that the syrup reaches the right temperature, you can start whipping the egg whites: when they are whipped until stiff and the syrup is ready, begin to incorporate it flush into the egg whites, continuing to whisk with whips.
Take back the gelatin (which by now should have absorbed all the water), pour it into the saucepan and let it melt completely over low heat, then also incorporate this into the egg whites, always continuing to whisk, and continue to whisk until the meringue has cooled.

At this point, if you want, you can divide the mixture to color a part: a few drops of dye will be enough, because marshmallows are usually pastel in color.

Sift cornstarch and powdered sugar mixing them together.
Pour half of it into a baking sheet lined with parchment paper, then spread the meringue over it (trying to keep the colors separate).
Sift the rest of the cornstarch and sugar mix over the meringue and let it rest for at least 12 hours at room temperature, uncovered.

Take back the pan, remove the mixture from the parchment paper, place it on a cutting board and divide it into cubes.
Sprinkle again with the mix of powders, in order to cover the parts just cut, then shake off the excess.

The homemade marshmallows are ready, you just have to serve them, or use them for your preparations.