We usually make our own MMF, but it seems to torn out to be a huge pain in the butt. We always get tons of powdered sugar balls in our fondant, we sit there and pick them all out and then the fondant is great, but its just so time consuming.

We grease the bowl, add the water, nuke for 30 seconds and then stir, repeat till marshmallows are melted. We grease the counter tops sift the powdered sugar and then pour the marshmallows on top... What are we doing wrong?

Just need to sift the 10X, same with American buttercream

Edited to say:
SO SORRY!! I just re-read that you said you DO sift your 10X
I've had similar situations when I dump all the sugar in all at once, so I would try adding small amounts of the 10X into all the melted mixture. Also just read that people are mixing in their food processor -sounds like a great idea to me!

what kind of sifter do you use, i don't sift mine, but when i have i bought the one that has a handle and the fine screen and use a spoon to sift it through, try letting the marshmallow cool a little that might help. try adding you sugar as you mix i use a bowl to mix mine in a large bowl and pull over the sugar as i need it and using crisco as i need it, it is easier to mix that way instead of all at once other wise i don't know what it is

I don't usually sift, but I generally make my MMF the day before and let it sit over night. I made 5 batches for a wedding cake last week and had only 1 or 2 tiny lumps to pick out. I also warm my MMF in the microwave after it's been resting overnight to make it easier to knead and roll.

Try and add in the powdered sugar a little bit at a time, instead of all at once, or in larger amounts.

This happens to me when I add cold powdered sugar (from the fridge) to the hot MM's...only then do I get "stones".

I try to remember, if using leftover powd. sugar, to take it out at least an hour prior to making.

PS...if you knead in the same bowl you've melted the MM's in, you'll have alot less mess to clean up.

I would try going the other way, add your sifted powdered sugar, smaller amounts at a time, to your melted marshmallows, instead of adding your melted marshmallows to your sugar. And I agree with Flour Pots, mix in the bowl you melted your marshmallows in, my fondant never touches my counter, lots less mess.