Hello all.  I want to try a buttercream recipe which calls for 500 grams of butter. However it's for the summertime so I want to use half shortening instead or butter.  Can someone guide me exactly how much butter and how much shortening I should use in grams, as I know the weight for each is different.  It would be 250 grams butter but how many grams of shortening? I read online that I would have to add liquid and so I am a bit confused on the process.  Thanks a lot!! 

Use exqactly as much shortening as you take out butter.  grams for grams :)  It's an exact replacement.  I have a wonderful recipe that uses 1/2 & 1/2 without any liquid added but it is in American cups.  If you can translate it into grams I would be perfect for your use.  https://www.cakecentral.com/recipe/22469/2-icing