Compound butters can be refrigerated safely for a week, but should be frozen after that. Although traditional sticks of butter are easy to measure, compound butters require slightly more leg work to be able to pull out exactly the amount you need.
Simply line a muffin tin with paper liners and using a measured cookie scoop, scoop in exact amounts into each muffin tin.
Freeze tray and when solid, remove and place in air tight container/bag and label with size increments for later use.
via Quick Tip: Use Compound Butters In Baked Goods | Apartment Therapy The Kitchn.