Marco Arment took the plunge, so you and I don’t have to:
Asprey’s recipe is 2 tablespoons of butter for 17 ounces of coffee, which is more caffeine than I can handle in the morning, so I made roughly a third of it: 6 ounces of coffee (AeroPress-brewed from 9 grams of beans), and about two-thirds of a tablespoon of unsalted butter.
Butter does not dissolve into coffee. It melts and floats on the surface in a thick, oily layer. I kept stirring it and swirling it around so I wasn’t just taking sips of butter off the top, but it was a losing battle.
My general rule for cooking is to add butter, Parmesan cheese (in big flakes), and cream — in that order. Coffee is the exception. The good news is that, based on this, I don’t need to try adding Parmesan.