I'd second the last post regarding Aux Armes de Bruxelles. It is living on rather than up to its reputation. I last went to Comme Chez Soi 3 years ago, and whilst it is a little cramped for space the food shows a marvelous dedication to delivering enjoyment without necessarily emptying your pockets. Probably the best soup I have ever tasted, and also the only restaurant where they come back and ask if you would like some more! However they have just lost one of their Michelin stars - personally I wouldn't let that put me off returning. Alternatively, if you want a slice of Belgium as opposed to Haute Cuisine, In't Spinnekopke is a traditional Tavern, that can offer a variety of beers as well as many hearty dishes, some cooked in beer (e.g. Lapin à la Gueuze, Carbonnades au Lambic). I can also recommend Armand and Ko, just off the other side of the Grand Place. Good Franco-Belgian bistrot, warm atmosphere and some good paysanne cooking, off the tourist radar, and for post-prandial delights, a cigar bar with excellent brandies.