I make a ton of it. My method is repeated by many on the cooking with cannabis forum. I personally use 28 grams of my fine manicured sugar coated trim per pound of butter. I put it in a crock pot, filling it with enough water to go over the butter about 1/4 to 1/2 inch, add the herb, and stir once an hour for 12 hrs. Strain through two layers of cheese cloth, available in the baking aisle of any grocery store, and put in fridge in large metal bowl.
Next morning I cut a small hole in the finished butter, and pour out the brown nasty water. I then lay the brick of butter on a cutting board, scrape the bottom with a spoon of any of the left over brown water crap, real clean. It's ready for use, and devastating. My patients LOVE the shortbread my wife makes, one batch uses the whole pound. One small slice and enjoy for the rest of the day.
Make sure you don't burn the butter, keep the crock on low all day long, and crack the lid to control temp. Don't let it boil! The shit you strain out is garbage btw.
Hope it helps......