Chop and wash the spinach - dry thoroughly.

Melt most of the butter in a saute pan. Add the spinach, toss well.

Add vinegar, if using. Toss the spinach well, to coat with butter and vinegar. Continue tossing as it cooks down.

When the spinach is almost cooked to your taste, add the strawberries. Toss spinach and berries, until the strawberries and heated and slightly softened.

Remove the vegetable mix to a plate. Swirl the rest of the butter into the liquid in the bottom of the pan, and then boil it a minute or less to just reduce it to a glaze: pour over the spinach.

Serve at once - this will not stand well.