Hello! I want to make a Minion cake for a birthday with white chocolate MMF with buttercream underneath it. I have made MMF and buttercream before but have never used them together. So kindly, please help me with the following questions:

1) I found a wilton discussion forum that said that adding 1 to 2 oz white chocolate to the basic MMF recipe (1 lb marshmallows + 2 lb icing sugar) makes it a white chocolate MMF? Is this ratio okay? If not, please tell me how I can turn my MMF into a white chocolate MMF.

2) I have made Wilton's American buttercream icing before, but it was very sweet, so i think MMF on top of that may become inedibly sweet. I know about SMBC and plan to make that but its not a crusting buttercream, right?

3) I fear that SMBC isn't a crusting buttercream and if I try to put my fondant on top of that, and mess up and need to adjust the fondant's position, it may mess up the icing. Am I correct? If this is so, then what other option do I have for making a not-too-sweet buttercream icing?

4) Can the amount of sugar be reduced in SMBC without changing egg whites and butter ratios? or would it affect the buttercream?

thank you

AI can answer the SMBC questions. You're correct, it is not at all a crusting buttercream, which those of us who use it love about it, among many things. Anyways...that's all I use, and I would suggest trying it out on regular shaped tiers a coupleof times before aattempting your minion. What you do differently when bringing fondant into the picture, is you chill the cake in the fridge or freezer for awhile, until the buttercream is very cold, and hard. Roll out your fondant, and then take your cake out of the fridge, and immediately cover the cake. Work quickly, but carefully. The cold will start firming up the fondant, and it won't take long before it's difficult to smooth out pleats and boo boos.

As far as messing with the ingredient ratios, don't. Follow the directions for your first couple of tries, then when you're familiar with the process, you can experiment. Google From Scratch Swiss Meringue Buttercream, and follow along with her extensive directions and explanations and her recipe.

AYou will not need to reduce the amount of sugar on smbc I promise you. If anything you're going to maybe want to add sugar to it

I add a cup of wedding white melted chocolate to my MMF.  Your ratio is correct, just need more chocolate for a baby smooth finish.