I make the marshmellow fondant and it turns out lumpy. I sift the icing sugar and yet when I mix the marshmellow and icing together i can see lumps of sugar in there. Why does this happen and how can I get rid of them once this happens??

Thanks

I dont know if any of these will help, but these are the best guesses I have.
First make sure you are pouring your melted marshmallow in to the sugar, not the sugar in to the marshmallow. I melt my marshamallow in a glass bowl in the microwave and pour about 3/4 of the sugar in another bowl and make a well in the center. Then pour the melted marshmallow in the well and mix as much as I can with a spatula. I then dust the countertop with the remaining sugar and dump the mixture out on the couter and kneed the rest of the sugar in. If it starts to get too hard to work with I put it back in the microwave for about 30-40 seconds until it softens up again and keep kneeding until its all mixed good.
Second, dont use the same bowls to make the next batch unless you wash them first. Continually using the same bowl will cause dryed pieces of sugar and marshmallow to get in to the new batch and no matter how much you kneed you cant get them out.
Hope these help!

I follow Peggy's process. Although I use a kitchen aid mixer works every time! http://whatscookingamerica.net/PegW/Fondant.htm