Add the cold water to the bowl of a stand mixer. Sprinkle the gelatin over the water and let sit for 10 minutes to bloom.
Grease an 8x8 pan and generously dust with powdered sugar. Set aside.
In a small saucepan, combine the water and granulated sugar. Stir over medium heat until the sugar dissolves.
Bring the mixture to a boil and cook until it reaches 240°F on a candy thermometer.
With the mixer running on low, very slowly pour the hot sugar syrup into the bloomed gelatin. Mix on low for 2 minutes.
Increase the mixer speed to high and whip for 10–15 minutes until thick, glossy, and fluffy.
Add the vanilla bean paste and mix just until combined.
Immediately pour the marshmallow mixture into the prepared pan and smooth the top. Dust lightly with powdered sugar.
Let set at room temperature for at least 6 hours or overnight.
Turn out onto a powdered sugar–dusted surface, slice into 16 pieces, and toss each piece in powdered sugar to prevent sticking.