1 cup confectioners sugar
2 tablespoons plus 2 1/2 teaspoons unflavored gelatin (like Knox- works out to be about 4 envelopes)
1/2 cup cold water
2 cups sugar
1/2 cup light corn syrup
1/2 cup hot water (about 115 degrees F)
1/4 teaspoon salt
2 large egg whites
1 teaspoon vanilla extract
Step 1: Oil a 9"x13"x2" rectangle metal baking pan and dust bottom and sides with confectioners sugar. Set aside.
Step 2: Pour cold water into large bowl that will be used with the stand or electric mixer. Sprinkle gelatin over water and let sit to softened.
Step 3: In a 3 quart saucepan cook sugar, corn syrup, hot water and salt on low heat and stir until sugar is dissolved. *Note- you really want to make sure sugar is dissolved well. If not, it may burn quicker in next step. Let it dissolve nice and slow. If there is any residual sugar left that hasn't dissolved you may end up with it burning.
Step 4: Increase heat to medium and boil mixture without stirring until candy or digital thermometer reads 240 degrees F, about 12 minutes. *Note, you do not want to stir the mixture, but you do want to keep an eye on it that the mixture does not start to brown and burn.
Step 5: While sugar mixture is boiling, place egg whites in a medium bowl and whisk until they just hold stiff peaks. Set aside.
Step 6: Once sugar mixture reaches 240 degrees F, remove from heat and pour over gelatin mixture. Stir by hand or on low setting on mixture until gelatin is dissolved. *I found mixing it by hand is better to know that all the gelatin that may be stuck on the bottom of bowl is mixed in.
Step 7: Using electric mixer or stand mixer beat mixture on high speed until thick, white and almost tripled in volume, about 6 minutes using a stand mixer and about 10 minutes using a handheld mixer. *Watching the transformation is pretty cool here!
Step 8: Turn speed to low and stir in egg white and vanilla extract just until combined.
Step 9: Pour mixture into prepared baking pan and sift 1/4 cup confectioners sugar on top. Chill uncovered for at least 3 hours and up to 1 day.
Step 10: Run a thin sharp knife around the edges of the pan and invert pan onto a large cutting board. Lifting up 1 corner of the inverted pan, with fingers loosen marshmallow and let drop onto cutting board. *After I ran a sharp knife around the edges I also used a spatula and gently helped push it up so when I turned the marshmallow over it came out. You may want to do this only in the even it does not come out the first time.
Step 11: Cut marshmallow as desired. Cut into large cubes or if using cookie cutter shapes, press cookie cutter firmly into marshmallow. While cutter is in place, take a knife and run it around the edges of cookie cutter. This will help the marshmallow to pop out easier.
Step 12: After marshmallow is cut into cubes or in shapes lightly toss in with confectioners sugar. Tap off any access. *I found after tossing it into confectioners sugar it was a little to much so I sifted confectioners sugar on top of them instead.
Step 13: To make chocolate dipped marshmallow, use chocolate melts and melt as per the package instructions. Let cool but not harden and dip marshmallows in as desired. *I used chocolate melts that can be purchased at the craft store (AC Moore). After chocolates are melted you don't want to dip the marshmallow in right away or it will start melting the marshmallow, let cool slightly before dipping.
Adapted from: Epicurious