I would like to add white chocolate to a French Buttercream recipe - which by nature is rather sweet (the chocolate)...can I decrease the sugar amount in the recipe without affecting the texture?
Since all recipes are essentially the same ratio, I would not mess with it, especially to sell it. This is a question for a university nutrition lab. We can give our opinions all day long and it means nothing. If you can find a pattern of French buttercreams with lower ratios, it may be ok. Remember that the yolk is much more likely to make someone sick.
I use French buttercreams more than Swiss, Italian, and custard bases. I understand about not wanting sweet because I don't like sweet either. Can you experiment with adding just enough to get the taste and not have it overly sweet?
Also, if this is for sale, I have found that customers like that extra sweet taste that I hate. I also don't like chocolate and I own a bakery. If I were you, I would find a recipe with tons of rave reviews, make it, and get others to taste it. It may be fine.
I can't get them in my area, but if you can find pasteurized eggs IN THE SHELLS (see FDA), this would eliminate the worry over the sugar/yolk ratio. Then you only need o make sure you have enough stability. Let us know what you find.
I use my French buttercream on a white chocolate cake. The taste is very subtle, not overly sweet at all. This is one of my best cakes. It has plenty of white chocolate in the cake.