Place butter in a heavy-bottomed saucepan and melt over medium-low heat.

Once melted, reduce heat and let it simmer gently. Foam will rise, then subside, as water evaporates.

Milk solids will sink and begin to brown at the bottom. When the liquid turns clear and smells nutty, remove from heat.

Strain through a fine mesh or cheesecloth into a clean glass jar. Let cool uncovered before sealing.