Thank you so much for this information. I definitely would not want to destabilize it since that is one of the great things about it. I did not know that about the temp not needing to go over 250 F. I am going to bookmark this.
Just play with the sugar and butter ratios until you find the percentages you like. I don’t use the standard ratios, like most bakers, I use ratios that suit my taste.
Here are some basic guidelines to flavor meringue buttercreams.
How to flavor Italian and Swiss meringue buttercream per batch based 300g egg whites.
Extracts: Mix in any flavor of extract to taste after butter is whipped in.
Vanilla bean & paste: for vanilla flavor I prefer to use vanilla bean or paste. Use 1/2 pulp of fresh vanilla bean or 10 g vanilla bean paste per batch.
Chocolate or white chocolate: melt and cool approximately 226g (8oz) of quality chocolate. Chocolate should be fluid, but cool. Mix into buttercream.
Purées: with purées, take care as too much can ruin the buttercream. Purée should be reduced to remove as much water as possible. Cook it down, then set it over a very fine sieve to drain for several hours.
Add small portions at a time to buttercream. The moisture in purée will vary by fruit, and batch by batch. So don’t assume you can add the same amount of purée of the same fruit. Also don’t forget to sieve purée with seeds and skins like raspberries and blueberries.
Alcohol: Bailey’s Irish Cream, Grand Marnier, amaretto, rum, whiskey, or whatever liquor you like to taste. But given it is a liquid keep it around 60mL (2oz) - 100mL (3.5oz) per batch. Again add a little at a time.
Coloring: buttercream can be resistant to color due to the butter. I would NOT recommend Wilton colors. Americolor gels mixed with a bit of their Flo-coat will create a smooth even colored buttercream. The flo-coat essentially converts the gel color to a food color that can be used in applications where moisture is an issue, like in candy.