Nothing is better than sautéing in butter.  The flavor of butter is incomparable.  But butter burns easily.  If the butter becomes brown before adding the vegetables or meat, throw it out.  It will make your food taste bitter and discolor any vegetables.

Try sautéing with a mixture of cooking oil and butter.  The cooking oil will retard burning and you will still taste the butter.

When you sauté, make sure the pieces are all the same size so that they cook uniformly.  The middle of the pan may be hotter than the edges so stir often.

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