Put the garlic, chilies, lime juice, sugar and water into a blender and whiz until you get a nice paste. Add the fish sauce and stir. Beat in the ground peanuts.
There are many variations to this sauce, and the beauty of making it yourself is that you can adjust the taste to your liking. Add more fish sauce if you want it to be saltier, or more water for the opposite effect. Add more sugar if you like it sweet and vary the amount of lime juice depending on how sour you want it .
There are no hard and fast rules here. The important thing is that you enjoy the sauce. Just make sure the basic ingredients are included in the recipe.