In a blender or food processor, combine all of the ingredients except the butter and blend until smooth, stopping occasionally to scrape down the sides of the container. Cover and chill the batter (for at least 1 hour; it will keep up to 3 days). In a 6-inch skillet or crepe pan over medium heat, melt the butter. Add 3 tablespoons of batter and quickly tilt the skillet in all directions until the batter covers the bottom. Cook for 1 minute, or until the crepe shakes loose easily from the skillet. With a spatula, flip the crepe and cook it for about 30 seconds on the other side. Repeat the procedure with the remaining batter, adding more butter if necessary. Stack the crepes between sheets of wax paper and cover with a clean dish towel until ready to serve, or store in a heavy-duty plastic bag for up to 3 days in the refrigerator or up to 4 months in the freezer.