I'm making a friend's wedding cake next month, and she would like it with fondant. I hate the taste of store-bought fondant so I decided to try to make my own. I'm just documenting the proccess here for next time, so that I can compare.
I used this recipe from A Spicy Perspective. However, the marshmallows I had on hand were large (instead of small), and the bag was 400g (13.5oz instead of 16 oz) instead of 16 oz. The marshmallows were.. also not the freshest.
In light of this, I used 6 TBSP of water, microwaved for 5 minutes in 30 sec. intervals, and used 28 oz. of powdered sugar along with 2-3 oz of corn starch. After kneading in the cornstarch (which is extraneous to the recipe), the fondant was still somewhat soft so I am letting it rest in the fridge over night. The mistake I made was adding all 6 TBSP of water at once; I should've stuck with the recommended 3 TBSP which probably would've been enough liquid to adjust for the dryness of the marshmallows.
We'll see how it feels tomorrow; I may have to add more cornstarch, but I'm hoping it will firm up once the fridge takes the heat from the microwave out of the fondant.
However, I did learn some important lessons:
1. Fondant is an excellent use of old dried out marshmallows! You just have to be more careful about adding enough (but not too much) moisture.
2. It is easier to add more moisture than it is to add enough powdered sugar/corn starch to make up for too much moisture.
3. If the fondant is too soft and sticky, adding more powdered sugar just makes it stickier - use cornstarch!