Spray 8 inch pan with nonstick cooking spray and lightly dust the sides with powdered sugar. Set aside.

Pour ice cold water into bowl of a stand mixer fitted with the whisk attachment. Add the Gelatin and allow to soften, about 3 minutes.

Combine water, sugar,corn syrup, agave nectar, and salt in saucepan. Heat over medium-high heat, stirring until sugar is dissolved. Cover; let bubble 2 minutes to remove any sugar crystals on side of pan.

Uncover saucepan. Attach a candy thermometer to the side of the pan. Cook, without stirring, over medium-high heat until the thermometer registers 240°F Fahrenheit.

Remove saucepan from heat. Slowly pour the hot candy mixture over the gelatin mixture in the mixing bowl and stir well to combine. The mixture will foam and bubble up in the bowl.

Mix on low speed. Gradually increase speed to high and beat until mixture is opaque and think, 8-9 minutes total. Add vanilla.

Continue beating mixture on high until thoroughly combined. The mixture should appear thick, yet have a spreadable consistency.

Immediately transfer the marshmallow mixture to the prepared pan. Using an oiled spatula makes it easier to work with the mixture.

Quickly and gently spread the marshmallow mixture evenly in the pan, applying more oil to the spatula, if needed.

Sift some of remaining powdered sugar, covering the top. Let stand, covering the top. Let stand, uncovered, 4-12 hours. If using collapsible pan, Open sides. If using baking pan, run an oiled knife along edges of pan to loosen sides of marshmallow mixture and invert onto cutting board.