I've been to Sonsie for Saturday brunch several times now, and one thing that keeps me coming back is the quality of the food. Although the service isn't the greatest, the food comes out the same each visit I take.
During the nicer days of spring and summer on Newbury Street, Sonsie opens up their floor-to-ceiling windows, allowing for customers who sit in the "cafe" part of the restaurant to feel like they're actually sitting outdoors. The tables are a bit small and maybe too cozy for some, but for a brunch for two, this place is intimate, yet casual enough for friends or lovers to brunch together.
It may be a bit too heavy for some people to have appetizers, main course, and dessert for brunch - but if you are a big eater, I'd say go for the steamed black mussels or the vietnamese spring rolls. Or if you don't find those appealing, the Asian Spinach Salad is perfect for two to share or one to eat as their main dish. It comes with fresh spinach, carrots, and shiitake nori rolls. The salad runs about 15 dollars and is very tasty.
If salads aren't your thing, go for their hot cubano. Definitely not a sandwich for dieters, but this comes with spicy pork, ham and cheese, and fried plantains that are cut very thinly. This sandwich is greasy but so good and decently priced at about 9 dollars. They have other sandwiches, such as the tuna melt, crabmeat sandwich, and veggie wrap. They also offer pastas and eggs served in almost every imaginable style.
If you're going to have the full brunch with appetizers, main dish, and a mimosa, you'll be spending about 40 bucks for lunch, but once in a while, it's well worth it. Sonsies brunch menu offers much more than some of the others on Newbury Street, such as Stephanie's or Charley's - I highly recommend it. Or make a reservation for dinner sometime and have some quality cosmos while you wait for your table at the bar.