Prepare a 9×13-inch pan by spraying it with non-stick spray and then dusting it with powdered sugar. Next, pour 1/2 cup cold water into the bowl of a stand mixer (or an electric mixer) and then sprinkle gelatin over the cold water. Soak for 10 minutes.

Combine sugar, corn syrup, and 1/4 cup water in a small saucepan. Bring to a boil and boil until temperature passes 250º F on a candy thermometer. Turn on your mixer and pour the boiling syrup in a slow stream into gelatin and mix as high of a speed as you can go. Continue to slowly pour the syrup in and mixing until syrup is gone.

When the mixture starts to become fluffy, add the salt and beat for 8-12 minutes, or until the volume stops increasing. Add vanilla and incorporate into mixture. Scrape into the prepared pan and spread evenly. (Note: if you need to press the marshmallow mix down, lightly oil your hands and spatula or bowl scraper).

After pouring marshmallow mixture into the pan, dredge top with powdered sugar, and cover lightly with a clean dish towel. Let mixture sit for four or so hours (I let mine sit overnight).

Last, remove marshmallow “slab” from pan onto clean cutting board, and with a sharp knife (or sharp pizza cutter), cut the marshmallows into whatever size you want. I wanted the marshmallows for hot cocoa, so I cut the marshmallows into 1- to 2-inch squares.

Sift together powdered sugar and corn starch into a large-ish shallow bowl. Dredge the marshmallows with powdered sugar mixture on all sides and place into a Ziploc bag or other airtight container.