Mix gelatin with 1/2 cup cool water in a small bowl, then stir in vanilla extract or seeds (no need to fully incorporate the vanilla seeds, if using; they will disperse later on).Advertisement
Grind sugar and sage in a food processor until the sugar is pale green and damp. Combine the sage-sugar with the remaining 1/2 cup cool water, corn syrup and salt in a large saucepan over medium heat. Stir with a fork until the syrup begins to simmer around the edges, about 5 minutes. Clip a candy or heatproof digital thermometer to the pot, increase heat to medium-high and simmer without stirring until the syrup registers 250 degrees F, 5 to 10 minutes more.
Meanwhile, lightly coat an 8-inch square baking pan with cooking spray.
Once the syrup hits 250 degrees , remove from the heat and transfer the thermometer to the bowl of a stand mixer. Scrape the hot syrup into the mixing bowl and let cool to 212 degrees , 8 to 10 minutes.
Add the gelatin mixture to the syrup and mix on low speed with the whisk attachment for 1 minute. Increase to medium-high and whip until roughly tripled in volume and beginning to ball up around the whisk, about 10 minutes. Scrape the fluff into the prepared pan, cover with foil and refrigerate until firm, about 1 hour.
To cut the marshmallows: Sift a bit of the confectioners' sugar over the top of the marshmallow, then invert the pan onto a cutting board and pry the candy loose with your fingers. Sift more confectioners' sugar over the exposed surface and rub until no longer sticky to the touch. Cut into 36 marshmallows with a chef's knife, wiping the blade clean as needed. Put the remaining confectioners' sugar in a sealable bag and shake a few marshmallows at a time in the bag to coat.
Make Ahead Tip: Prepare through Step 5 up to 3 days ahead. Store finished marshmallows airtight at room temperature, with wax paper between layers, for up to 2 weeks.
Equipment: Candy thermometer
1 other carbohydrate