In a small bowl, add in the 2 packets unflavored gelatin and 1/2 cup of water. Let bloom.
In a large saucepan, add in the 3/4 cup granulated sugar, 1/2 cup light corn syrup, the remaining 1/2 cup water, and 1/4 teaspoon salt. Place over medium heat and let it come up to 240 degrees F.
Add the 3 ounces strawberry jello mix to the large saucepan and stir to combine.
Add the bloomed gelatin to a stand mixer bowl and slowly begin to pour the hot sugar into the bowl. This will help dissolve the gelatin.
Begin whipping the mixture with the whisk attachment for 8 to 10 minutes until fluffy and stiff.
While the marshmallow mixture is whipping, prepare the pan.
Lightly spray an 8x8 inch square pan with nonstick baking spray.
In a small bowl, combine the 1/4 cup powdered sugar and 2 tablespoons cornstarch. Reserve half of the mixture to dust the top of the marshmallows.
Dust the greased pan with the powdered sugar and cornstarch mixture.
In the last 1 minute of beating, add the 3 teaspoons strawberry extract and 2 drops red gel food coloring. Continue to beat.
Pour the marshmallow mixture into the prepared pan.
If you want a red swirl in your marshmallows add an additional 1 to 2 drops of food coloring on either side of the mixture and use a skewer to swirl it around.
Add the remaining powdered sugar/cornstarch mixture on top of the marshmallows. Spread it to cover all of the marshmallows.
Let the marshmallows rest for at least 4 hours to firm up before cutting. Overnight is best.
Using a sharp knife or pizza cutter, cut the marshmallows into 12 pieces. If the marshmallows are sticky, dust the knife with some of the powdered sugar/cornstarch mixture.
Toss the marshmallows in additional powdered sugar so the sides aren’t sticky.
Notes
Storage: Store in an airtight container at a cool room temperature for up to 2 to 4 weeks.