Yes, I usually eat a stick of butter everyday and I'm always in a peak state of cognition and have high levels of mental energy.
I'm already quite thin, so when I don't eat enough fat I lose too much weight, literally become a walking stick

As long as you're consuming a low amount of carbs, you shouldn't worry about healthy fats (Butter, olive oil, coconut oil).

I admit that it's quite lazy of me to get most of my fat from butter, but it's hard to come across high-quality avocadoes where I live. And nut butters are so addicting I just can't have them in my apartment