Add all ingredients to a blender, and blend for one minute. Scrape down sides with rubber scraper then blend an additional 30 seconds. Refrigerate at least an hour. To cook, heat a small frying pan or crepe pan on medium heat. Lightly brush bottom with butter. Scoop out 1/4 cup batter and pour into pan, tipping pan to coat bottom of pan. When lightly browned, flip over with spatula. Lightly cook on other side then remove to plate.