Up and down the West Coast — in Seattle, San Francisco, and Los Angeles — recent immigrants are reviving the old Russian neighborhoods with new restaurants, bakeries, and food stores. And an old classic, chicken Kiev, is making a comeback on Russian restaurant menus. Capturing a heart of melted butter in a slab of chicken breast was once considered a test of culinary skill — getting a good seal is the secret. Finishing the dish in the oven, rather than frying it in deep fat, is a healthy step forward. One caveat: Chicken Kiev spurts when cut, so warn your guests.