I've not tried butter in coffee (yet) but I bloody love a bit of french stick with half an inch of butter spread on it dunked in coffee.
I saw some French cunt do it in Amiens in 1992 for breakfast and it has stuck with me ever since.
Still - Quarry eh...Brilliant stuff.
It's quite a thing in America, you know, the frontier types. I've been watching a few American woodsmen lifestyle you tubers lately. They do all manner of shit from making wooden houses, catch/kill/eat and reviewing axes.
One of them did a video on "bulletproof" coffee. Basically coffee filtered over butter and high omega three oil then whizzed in a blender. It's nice, I can recommend it.
I'd offer you a beer, but I've only got six cans.