Pour ½ cup cold water into stand mixer bowl fitted with whisk attachment. Sprinkle in the powdered gelatin and let it dissolve and soften. Add in the scraped vanilla bean seeds.
In a heavy bottomed saucepot fitted with a candy thermometer, combine the rest of the water, sugar, corn syrup and sea salt. Stir to combine and bring up over medium heat. Gently stir if needed, but try to leave untouched. Bring the mixture to a boil and cook until it reaches 240° F, soft ball stage.
Once mixture reaches 240° F, immediately remove from heat.
Turn stand mixer on low to break up the gelatin. Slowly pour the hot sugar mixture into the bowl. Try to do this in one slow steady stream. Once all of the sugar is poured in, gradually begin to raise speed up to high. Let mixture beat for 10-12 minutes or until it is light, fluffy and white in color. Add vanilla and beat for 1 more minute.
While your mixture is whipping, prepare a square 8x8 baking dish. Spray with a little cooking spray and line with parchment paper. Make sure the paper hangs over the sides, this ensures easy removal. Using a fine mesh strainer, sift the powdered sugar over the prepared dish. Set aside until needed.
Once the marshmallows are ready, lightly spray a silicone spatula and scrape the mixture into the prepared dish. Make sure it lies evenly; you may need to wet your hands with a little water to push it down. Sprinkle the remaining powdered sugar on top and let sit, at room temperature for a couple of hours.
Cover the dish with plastic wrap and let sit overnight. The next day you can cut them into squares and dust with powdered sugar. Store in an airtight container for up to 3 days.
Recipe Courtesy of Megan Mitchell