In a minor PSA: Grass fed butter is not really much different than most other butters (actual butters, of course, not "not-butters"). It might be marginally different in some nutrients, but, by and large, it's still much the same butter fats.
It will make basically everything delicious, of course, but don't go thinking you can call something "diet" if you use grass fed butter, or go around saying "you can have as much as you want because it's grass fed butter, not regular butter".
tl;dr: Butter is butter.