It's hard to believe I've had The Dessert Blog for so long and haven't yet mentioned Finale. For those not in the Boston area, Finale is a dessert restaurant with a few locations in and around the city. It's very high end, with $10 "plated desserts" and a large selection of dessert wines, dessert martinis, etc. There are also a few appetizers and such, in case you're too hungry for just a dessert, but really the focus is on the sweets.
Last night, I went there with my wife and a couple friends, and I ordered one of my favorites: Molten Chocolate. I've seen (and tasted) this basic idea of a chocolate cake with a warm liquid/gooey chocolate center in many restaurants, but this is by far the best version I've had. High quality chocolate, exactly the right consistency inside and out, a Valhrona chocolate sauce, and a small but high-quality scoop of gelato (coffee by default, but I substituted vanilla). Combine that with a nice glass of sherry, and you really have yourself a treat. A treat that costs $20+, mind you, but a treat nonetheless.