I thought I read someplace on here that you can mix your say raspberry filling with the buttercream. Has anyone done this? What ratio did you use so the filling didn't become too loose?
Sure! I mix raspberry jam into swiss meringue buttercream all the time for a filling or icing. Just add a bit at a time until you get the color and flavor you want without making it too runny. If you're using it for a filling, you may want to pipe a stiff buttercream dam around the edges to keep the softer filling in place.
I just made a cake mixing strawberry sleeve filling with Indydebi's BC. I just kept mixing "enough" to get the right flavor & consistency. It was thin, but I made a stiff damn and didn't have any problems at all.
I will say that it was the first time trying the sleeve fillings. Without the BC I thought it tasted disgusting! Ugh! But it was delicious with the BC