Make the marshmallow mix by mixing the ingredients together in a bowl and set aside.
Add the gelatin and half the water together in a stand mixer and set aside. Attach the whisk attachment to the mixer in the meantime.
Mix together the remaining water, sugar, corn syrup, and salt in a saucepan and heat on medium-high. Allow to boil for about 10 minutes, or until the mixture reaches 240F.
Turn on the stand mixer on low and drizzle in the sugar and corn syrup mixture into the bowl. Be careful not to let the mixture splash on the sides or out of the bowl.
Beat the mixture on medium speed for about 15 minutes, or until the outside of the bowl feels about room temperature. Add in the vanilla and beat for another minute.
Prepare your containers while the mixer is still beating. Grease 20 small Dixie cups if you are making pops, or grease a 9x9 baking ban and generously coat with the marshmallow mix. If you are using Dixie cups, please make sure the rims of the cups are also greased and coated in the marshmallow mix.
Once the marshmallows are ready (the mixer is at room temperature and you've added your vanilla), either pour the marshmallows into the pan, or grease an ice cream scoop then coat in the marshmallow mix (or you can attempt to use a greased pipping bag). Use your ice cream scoop to fill the Dixie cups with the marshmallow. Place a lollipop stick in the middle of each Dixie cup. Top with more marshmallow mix (do this for both the pan and Dixie cup method).
Place on the counter for at least 3 hours, or preferably overnight.
Remove the marshmallows from the Dixie cups. Or remove the marshmallows from the baking pan and cut into large cubes using a greased knife.
Place the sprinkles in a bowl. Place a sheet of parchment paper on a flat surface. if you are coating the marshmallow pops.
Melt the white chocolate by placing in a microwave-safe bowl and heating for 30 seconds at a time and mixing the chocolate between each 30 second interval.
Working quickly, dip the marshmallows into the white chocolate. Allow it to drip off any excess white chocolate, then dip into the sprinkles. Place on the parchment paper. I found the marshmallow mix dries out the white chocolate quickly, so you don't have a ton of time before you can dip the marshmallows in sprinkles before the chocolate is too hard to stick. You can reheat the white chocolate as needed.
Notes
Use a candy thermometer for an accurate reading of the sugar because it is important not to go over 240F I highly recommend leaving the marshmallows overnight for the best results. Store marshmallows in an airtight container for up to 6 months at room temperature. Do not store in the refrigerator or freezer. Make sure your knife is greased before cutting the marshmallows otherwise the marshmallows will stick to the knife too much to cut.