I just made my first visit to the Cafe Besalu in Ballard (24th Ave NW at 59th St). A friend who just returned from Paris told me that Besalu was as good as she had in Paris. I'm in Paris twice a year and have a pretty good idea of what great croissants are like.
She was right. Besalu's croissants would be better than average in Paris, in fact just below the top bakers. Very light and flaky with just enough butter and the right flavor.
On a good day Le Fournil (Eastlake near University Bridge) is the equal of Besalu. I have also found them unpredictable. Some days there is little flakiness. In fairness, I only visited Besalu once, so it's only from my friend's recommendation that I can imagine they are more consistent.
Don't go late to Besalu or Fournil. By noon or 1 pm they'll be out.