A recipe passed down can survive a change made for the person eating today.

Faithfulness to the written version was never the point of a family recipe. It was made to feed particular people, and the people change: someone cannot have the butter now, someone else cannot manage the heat. Adjusting for whoever is at the table continues the thing rather than breaking it, because the eater was always the subject. A dish nobody can eat has been preserved into uselessness.

Make the change and keep making the dish. Write the reason beside the recipe so the next person knows what was adapted and why. Traditions last by staying usable, not by staying untouched.