Just wondering how long I can let a cake covered in marshmallow fondant (and coated and filled with buttercream) sit out? I have heard 3-4 days. I know you're not supposed to refrigerate fondant to avoid beading/sweating- is it the same for MMF? I really don't want to poison anyone! Thanks for the info in advance

As long as you don't have perishable fillings you can definitely leave it out at room temperature for as long as it lasts before someone eats it all....in my house it's usually about 3 to 4 days.