In a large frying pan, melt 1 pound unsalted butter over very low heat; this should take about 15 minutes. Increase the heat to medium. White foam will begin to form on the surface and the butter will start to crackle.
This indicates that the moisture is beginning to leave the milk solids. Cook for 10 minutes without stirring.
When the moisture is completely gone, the crackling will stop and the foam will subside.
Using a wooden spatula, stir the liquid constantly until the butter solids begin to brown. Immediately turn off the heat and let the brown residue settle to the bottom.
When the melted butter is cool, pour the clear liquid into a jar through a double layer of cheesecloth.
One pound of unsalted butter will yield 1 1/2 cups of usli ghee. Ghee will keep in a well-sealed jar for about 2 months at room temperature and 5 months in the refrigerator.