This is the hands down best way to make butter, there are lots of ways to do it. I learned the following technique form an issue of high times in the late 90's and it works better than any other way I have tried. The best thing about this technique is you get close to maximum thc extraction and remove the risk of burning your butter or oil.
You will need:
12 quart+ pot
1-4 sticks of butter(depending on desired strength and quantities)
7-28 grams of high quality herb
pasta stainer
good sized piece of cheese cloth(you can also use an old t-shit or towel if ya dont have cheesecloth on hand)
Get you water heating and start breaking down your herb, use a hand grinder. You want it to be pretty fine, but dont worry about powdering it.
When the water gets to a rolling boil add the butter. My rule on potency is to use .5-1.0 grams per serving. Use a stick of butter per 7 grams, the fat in 1 stick of butter will hold much more that the thc from 7 grams however, just depends how strong ya want them to be. I usually use between 7-14 grams per stick of butter.
Once you have added the butter and you boil is rolling again add your herb and set a timer for 2 hours. Leave the pot partially covered and make sure to check it every 15 min or so. Dont let it boil over, and be sure to add a little more water if you start boiling off to much of the liquid.
Get you strainer setup over a clean pot of aprox. the same size. When the time is up pour everything through the strainer into the clean pot making sure to remove as much of the plant matter as possible. Once the boiled herb cools a little bit, ring as much liquid as you can outta the plant matter, as it will still contain a little bit of the herb butter that you have been working so hard for.
If you are in a hurry, make a cold water bath in your sink(use ice liberally, it takes a lot to cool boiling water), or you can just throw a lid on the pot and put it into the refrigerator over night. The butter will float to the top and solidify. take a good sharp knife and cut the disc of butter away from the sides of the pot then you can usually pull it out in a few big chunks. I then will pour that liquid through the strainer setup again to catch the little pieces of butter that have broken off of the larger cake.
I realize this is a bit more work that the standard stove top method, but it does work VERY well. You get maximum extraction, you wont burn the butter ever, you wont have to stand over a pan for an hour constantly stirring and checking temp, and you also get a better tasting butter. When you cook the herb in just straight butter or oil, all sorts of things other than thc get pulled into the oil. With the boiling technique, you also get a better tasting butter. The water grabs a lot of flavors and pigments that would normally end up in your butter, the result is a cleaner tasting butter that still produces a great high.
I hope this is helpful. I have been using this exact method for over 10 years, and it works great every time.