This is another recipe I use a lot at home :D
This is not my recipe though, it comes from Gretchen Price at Woodland Bakery in America, all credits to her!!
Her recipe has worked every time for me and makes a less sweet alternative to a traditional American buttercream. It takes longer of course, but its worth it in the end. It is basically a Swiss meringue with added butter to make it hold its shape easier (the raw egg whites are totally safe to eat though, theres more about that on the recipe).
I won’t actually repost this because there is so much more information about troubleshooting/substitutes and stuff on the original recipe
Also subscribe to her on YouTube for more awesome recipes!