Before starting on these marshmallows I advise that the pans in which the marshmallows are set are prepared. They were first coated in baking spray and then dusted in a mixture of corn starch, powdered sugar, and cocoa.
In a small bowl, the gelatin was sprinkled over ½ cup of water to allow the gelatin time to bloom and soften.
While the gelatin is softening, the egg whites and sugar were added to the standing mixer and whipped until very thick. The mixer was then turned off while I attended the next steps.
In a medium saucepan fitted with a candy thermometer, I mixed the sugar, corn syrup, and 1/3 cups of water. This was heated over medium high heat.
When the sugar mixture reached 240°F, the mixer was started again on high speed. As the sugar reached 245°F, it was poured into the whipped eggs carefully to avoid hitting the whisk so it wouldn't splatter all over the mixing bowl.
Into the same pot I used for the sugar, I added the bloomed gelatin, salt, and espresso powder. The residual heat of the pot should be enough to melt the gelatin and dissolve the espresso.
When fully melted, this last concoction was added to the mixer and everything continued being whipped until fully cooled. Unlike the marshmallows that don't use egg whites, these are much more forgiving timewise. You want to make sure you really do whip this non-stop until it is fully cooled.
Finally, the now cool mixture was spread to the best of my ability between the two prepared pans and allowed to set overnight, uncovered.
Cutting these up was not easy, it was like they didn't want to be pretty. I used a coconut oiled knife to try to get clean cuts but to no avail. I will have to try using a pizza cutter or scissors next time.