Flavoring butter with a small bit of lavender is a subtle way to enhance these muffins. If the lavender were added to melted butter then cooled, its flavor would be stronger than this preparation.

MAKE AHEAD: You'll have a small amount of lavender butter left over. The butter can be prepared a week or two in advance; refrigerate or freeze. Its lavender flavor will strengthen after a week. The muffins are best served the same day they are made.