Adapted from Lisa Yockelson. Be sure to use a strong mixer with this recipe: I can only vouch for a Pro level. Do NOT attempt it with a hand mixer.
Ingredients
2 envelopes gelatin (I always use Knox)
⅓ cup + 3 T cold water
1⅓ cups + 2 T granulated sugar
1 cup + 3 T light corn syrup
large pinch salt
9 T cold water (separate from water above)
2 t vanilla extract
2 t peppermint extract
several drops peppermint oil or approx. 2-3 full size candy canes, crushed
approx. ½ cup powdered sugar
Instructions
Choose a 7 or 8 inch square nonstick pan (I have only tried nonstick--may work fine with others, I cannot confirm; Yockelson prefers thick marshmallows with a 7 inch square pan but I like smaller marshmallows plus I already owned an 8 inch square pan). Dump a heaping ⅓ cup of powdered sugar into the pan. Shake it from side to side and use your fingers to "coat" the sides of the pan. The powdered sugar will stick in patches, which is fine. Leave it in the pan; it may be uneven (see my picture up above).
Place the gelatin in the bottom of the mixer bowl. Prepare the water measurements and set aside the larger water (1/3 cup + 3 T) beside it.
Find a heavy bottomed, preferably copper or stainless steel, 2-3 quart saucepan. Add the 9 tablespoons of water, light corn syrup, sugar and salt to the pan. Attach a candy thermometer to the side of the pan--do not let the actual thermometer touch the bottom of the pot. Place the pot on low heat and cover it.
Dump the other water over the gelatin--it should sit for 15 minutes.
While the gelatin is soaking, stir the sugar mixture 2-3 times, very gently each time. When the sugar has dissolved, remove the lid and turn the heat up to high. From here on out do not stir or otherwise bother the sugar. Keep an eye on the thermometer; you want to boil the sugar to 248-250 degrees F.
When the sugar mixture reaches 245-248 F, slowly pour it in to the mixer bowl with the whip attachment mixing on the lowest speed. Be very careful to not let any of the boiled sugar touch your bare skin.After the sugar is all in the bowl, slowly increase the speed to medium low and beat for 1 minute. When the mixture is totally blended, increase the speed to high and beat for 2 minutes. Reduce the speed back down to low and add the extracts and oil/crushed peppermint. Increase back to the highest speed again and beat for 8 minutes.
During this time the mixture will becomes more opaque and whiter. It will also become much, much thicker. I have included a series of pictures that I took--you cannot see the whip attachment it is moving so fast, so the pictures are a little blurred, but it gives you the basic idea. I check the back of my mixer every so often during the 8 minute beating--if it should ever get dangerously hot, well, I guess either quit or cross your fingers.
If you want to color the marshmallows, reduce the heat to medium low, grab the color you want, reduce the heat to low, and squirt some in. For a more swirled effect, like what I have, only let it run a few seconds. Let it run longer to completely color the marshmallows. See my notes above for more comments on coloring marshmallows.
Here comes the exasperating part--but with practice it will become less tricky. Quickly undo the whip attachment and set it aside--accept that you will lose some fluff sticking to it. Using a very sturdy spatula that has preferably been dredged in powdered sugar, quickly and firmly scrape the marshmallow fluff into the prepared baking pan. It will astound you how fast it sticks to everything! When I first started making marshmallows I saved that sticky fluff like it was gold and spent long minutes scraping it into a cup of hot chocolate. Nowadays either the kids lick it off or I just throw it in the sink and accept it as lost.
Take a few tablespoons of powdered sugar and sprinkle it around the edges of the pan, right up against where the marshmallow meets the sides of the pan (see picture above).
The marshmallows now need to cure by sitting out at room temperature for 6-8 hours. If it is particularly humid, it may take longer. At the end of the time, take a narrow spatula and run it along the sides of the pan to loosen the marshmallows. You will be astounded at how it all lifts out in one gigantic marshmallow cake--quite easily. Place the marshmallow on a wooden cutting board and have a bowl of (yet more) powdered sugar sitting at the ready. Slice the marshmallows with a large chef's knife, dredged in powdered sugar. Use a swift, decisive, downward slicing motion, kind of like mincing an herb but more time between slices. Do not try to saw at the marshmallows. The marshmallow center will stick to the knife--just pull it off and keep going. As you slice each individual marshmallow, dredge it in the powder sugar and set it aside in a single layer.
Store in a single layer in an airtight container. Marshmallows for plain eating are good for at least a week. Marshmallows for dipping and melting in hot chocolate will last far longer, since a little drying out is not noticeable.
Recipe by The Spiced Life at https://www.thespicedlife.com/extra-creamy-peppermint-marshmallows/