We'd like Chapeau!'s classic French cuisine -- dishes as simple as textbook-perfect onion soup and sole meunière and as complicated as ballotine of foie gras and cassoulet -- at any price. But we like it best when we can run riot through the seasonal, evolving menu and choose our own three-course prix fixe for just $29.75 (plus a few modest supplemental charges, such as $1.75 for the foie gras or $2 for a plate of five cheeses). Even with the supplements, it saves you about $10 off the a la carte prices. And if you find yourself hungry between 5 and 6 p.m. Tuesday through Thursday, there's the Gallic Clement Street equivalent of an early-bird special: three courses for $19.50. It's three-star cuisine at coffee shop prices.