Spray a 9- x 13-inch pan with spray oil or line with parchment paper to keep marshmallows from sticking to pan. Put the gelatin and 3/4 cup cold water in the bowl of a stand mixer. This will bloom or activate the gelatin while the sugar mixture heats up.

Mix granulated sugar, corn syrup, salt and 3/4 cup water in a saucepan. Heat over medium heat and place a candy thermometer in sugar mixture. Once the sugar reaches around 238°, remove from heat and slowly and carefully pour the hot mixture into the gelatin with the mixer on low. Slowly increase the speed of the mixer every few minutes until the mixture is stiff and shiny, about 10-15 minutes. Pour the mixture into the pan and let it set until it is firm, 4-12 hours.

Once firm, dust the top of the marshmallows with powdered sugar or toasted coconut. Flip the marshmallows onto a cutting board and dust the other side with powdered sugar or toasted coconut. Using a sharp knife or cookie cutter, cut the marshmallows into desired shape and toss in powdered sugar or toasted coconut. They will be sticky. Keep in an airtight container.