Winter's Touch

Your expertise with the magic arts, and more specifically frost magic, has granted you the ability to augment spells you cast that don't normally have cold effects. During a Short or Long Rest, you my select a number of spells you have prepared, up to your proficiency bonus, and switch their damage type to cold. The damage of type of the spells which you augment this way must be fire, lightning or thunder.

Additionally, as a Bonus Action on your turn, you may switch the damage type of any spell you cast to cold. Once you use this feature, you cannot use it again until you finish a Short or Long Rest.