Bloom the Gelatin: In the bowl of a stand mixer, combine 3 tbsp gelatin with ½ cup cold water. Let sit for 5–10 minutes to bloom.
Cook the Syrup: In a medium saucepan, combine 1 cup honey (or maple syrup), ¼ cup water, and ¼ tsp salt. Heat over medium heat. Clip a candy thermometer to the side and cook until the mixture reaches 240°F (115°C) (soft-ball stage). Do not stir.
Whip the Mixture: Start the mixer on low speed, and carefully pour the hot syrup into the bloomed gelatin in a slow, steady stream. Increase to high speed and whip for 8–12 minutes, until thick, glossy, and tripled in volume.
Add Vanilla: In the final minute of whipping, add 1 tsp vanilla extract.
Pour and Set: Quickly pour the marshmallow mixture into a parchment-lined and lightly greased 8x8-inch pan. Smooth the top with a spatula. Let set at room temperature for 4–6 hours (or overnight).
Cut and Dust: In a bowl, mix powdered sugar and arrowroot powder. Remove marshmallows from the pan, cut into cubes using a greased knife or scissors, and toss each piece in the dusting mix to prevent sticking.
