"Ghee is a class of clarified butter that originated in ancient India and is commonly used in South Asian cuisines, traditional medicine, and religious rituals." -Wikipedia
In today's world there are a lot of people who cannot tolerate dairy, myself included. One of the good things about ghee is that, when it is prepared correctly, the milk proteins are removed. This means that many people who cannot tolerate butter can tolerate ghee. Basically, it is the best of both worlds: the benefits (and taste!) of butter without the casein and proteins that you may react to.
You can find ghee in the store:
... but I suggest you make it yourself if you have lactose intolerance as I have found that it is very easy and a lot more of the milk proteins seem to be removed when I make it myself than when I purchase it at the store. The exception to this would have to be Tin Star Food's ghee. I have heard awesome things about their ghee from people who do not tolerate dairy well. This isn't to say that other brands' ghee isn't great, I just haven't tried it so I don't want to speak to it. The brand of ghee you see above ended up making me decide to stop being lazy and make some ghee at home again. That's good for you guys though because you can now see how I make it!
1. Place butter in sauce pan over low heat. I couldn't find grass-fed unsalted butter so I am using a salted variation.
2. Check on butter regularly over the next 2-3 hours, stirring as necessary. It does take a long time to make but you don't have to stand over it the whole time. I often put it on and then go clean my house or do homework, checking on it about every 20-30 minutes.
3. When you see the milk solids have settled to the bottom and begun to brown so your liquid butter has become golden in color it is time to remove it from the heat. When it gets close to this point though I suggest you stick close to your pot to make sure you only slightly brown the solids verses burning them. I should have left this batch on the stove for a few more minutes so that the milk solids would brown a bit more but I was running behind. It still came out beautifully though.
4. Strain the liquid through cheesecloth into a non-plastic container (I have melted a plastic one before... oh the mess!). The milk solids will remain in the cheesecloth while your ghee will strain through the mesh to the container beneath.
5. Place your ghee in a container. If it has been prepared properly you won't need to refrigerate it and it will last for months.
The unrefrigerated ghee is on the left but if you do store it in the fridge it will look like you see on the right.
One thing to understand about ghee is that the flavor is more intense than the butter you started with. I would suggest adding a little at a time to your dish when first learning to cook with ghee for this reason. Another, awesome, thing to know is that the smoke point is incredibly high so it is great for high heat cooking like sautes and stir fries! I have heard it said that 'you flavor with it like butter but cook with it like oil' and I find that to be fairly accurate but I tend to use less ghee than butter when flavoring with it due to my personal preferences on taste.