Bloom: Prepare a 9x13-inch pan by lining it with parchment paper both directions. Allow the sides to drape over for easy handling. Dust the bottom lightly with arrowroot powder. Set aside. In the bowl of a stand mixer, add ½ cup of filtered water and sprinkle gelatin over the water to "bloom". Whisk to combine and set aside.

Heat: In a thick-bottom saucepan over high heat, heat remaining water (½ cup), honey, and salt together. Bring to a simmer and reduce heat to medium. Continue to simmer the honey mixture over medium-high heat for approximately 8 minutes. Watch the honey mixture carefully so it doesn't boil over and is gently simmering. It must be simmering the entire time. Avoid stirring it. If you see the honey mixture rising up, slightly reduce heat, then gradually bring it up again so it's simmering again.

Whisk: Assemble the stand mixer with a whisk attachment and position the bowl with bloomed gelatin. Turn the mixer on low setting, breaking up the gelatin. Gently and very slowly, pour the hot honey mixture in a thin stream, ensuring it pours down the sides of the bowl and not directly into the gelatin. Take your time here. It should take you about 90 seconds to pour out the entire honey mixture in a thin stream.

Beat: Gradually turn mixer to high setting and continue whipping until mixture has increased in volume and is thick and glossy and stiff peaks form. (approx. 8 minutes) Add vanilla powder in the last minute, if using. Take care not to overwhip as it will be too tacky to transfer to the pan.

Set: Transfer marshmallow fluff to the prepared pan and spread evenly across with spatula. Metal icing spatula works best. Set aside at room temperature for at least 4 hours but overnight is best.

Cut: Dust the top of the marshmallows with arrowroot. Remove the marshmallow by lifting the parchment paper flaps on the sides and transfer to a large cutting board. Carefully, remove paper from marshmallow edges and coat the edges with more arrowroot for easier handling. It should release easily. Flip over the marshmallow and sprinkle the bottom side with arrowroot if necessary. Cut to the desired size. Gently toss all marshmallow pieces in loose arrowroot powder.