This is another fine, simple Italian recipe using pearl onions. Supermarket frozen onions work fine in this recipe, and they save a ton of time and sore thumbs from peeling.
I keep a bag or two of frozen onions in the freezer for this and similar recipes because they go with so many dinners, especially winter cooking. If you will be serving these with meat, consider replacing the dry vermouth with chicken stock. Of course, you can use just water, too.