Put the butter into a small saucepan over the lowest heat. Cook until the bubbling stops. Skim the foam from the top, and pour away the clear butter from the solids at the bottom of the pan. You now have clarified butter.
Wipe out the saucepan to get rid of the milk solids, and return the clarified butter. Heat it over medium heat for about a minute, then add the garlic, parsley, and crushed red pepper. Cook until the garlic is fragrant--which may be less than a minute. Turn off the heat and let the sauce sit for a minute. Then add the lemon juice or white wine (careful! it may splatter!). Whisk a bit to emulsify the liquid into the butter.
