Instructions

• Line an 8×8 or 9×9 square baking pan with parchment paper, leaving an overhang on two opposite sides to lift the marshmallow out later. Generously dust the parchment and the interior sides/corners with powdered sugar so surfaces are coated.
• In the bowl of a stand mixer, dissolve 1 tablespoon instant espresso powder in 1/3 cup cold water. Evenly sprinkle 2 packets unflavored gelatin over the espresso water and let sit at least 5 minutes to bloom.
• In a heavy saucepan combine the remaining 1/4 cup cold water, 1 1/2 cups granulated sugar, 1/2 cup corn syrup, and a pinch of salt. Stir over medium heat just until the sugar dissolves. Attach a candy thermometer to the pan.
• Bring the mixture to a boil. Once boiling, cover the pan and let it sit covered for 2 minutes. Remove the cover and continue boiling, without stirring, until the syrup reaches 238°F (soft‑ball stage), about 7 to 8 minutes.
• Fit the mixer with the whisk attachment and set it to low. Very carefully and slowly pour the hot sugar syrup down the inside of the mixer bowl into the bloomed gelatin mixture, taking care to avoid splattering.
• Increase the mixer speed to medium‑high and beat the mixture for 12 to 15 minutes, until it becomes thick, glossy, and lukewarm to the touch.
• Add 1 teaspoon vanilla and beat on low just until incorporated (a few seconds).
• Transfer the marshmallow mixture into the prepared pan. Use a spatula dusted lightly with powdered sugar to spread it evenly (the mixture is very sticky).
• Let the marshmallow sit uncovered at room temperature for at least 3 hours, or until fully set.
• Use the parchment overhang to lift the marshmallow from the pan. Dust the top with powdered sugar, then cut into squares with a knife dusted with powdered sugar (re-dust the knife or the surface between cuts as needed).
• Dust the cut marshmallow squares liberally with powdered sugar so they do not stick together. Store in an airtight container for up to 5 days.