Such a magnificent mansion is hard for a kitchen to live up to, and Fourways has tried several formulas. Its newest bid for grandeur was importing a chef from England and backing him up with a crew of his choice. I'm sorry to report that despite an exciting menu with "symphonies of seafood" and "health- conscious dishes" my last dinner was pretty ordinary.

Fourways leads you to expect so much. First there is the imposing entrance with valet parking. Inside the grand foyer there is a glorious display of ripe-looking cheeses, and spectacular seafoods such as giant fresh shrimp and scallops with their roe. The dining rooms are sumptuously furbished, and formally dressed waiters serve with dignity. And the leather-bound wine list provides interesting choices (with particular depth in, oddly, Alsace wines); but its prices are uniformly high.

The menu describes "maize- fed chicken with a red bell pepper sauce and a fondue of leeks" and breast of duck with lime and mango, smoked trout mousse with smoked salmon, specials such as game sausage with sage butter or veal steak with woodland mushrooms. And the ingredients are indeed first quality -- the veal in its pale prime, the foie gras fresh. But too many things have fallen flat in the preparation: Aspic for the trout mousse lacked any discernible flavor, as did several sauces. Game sausage was dry and too finely ground. Worst of all, those beautiful shrimps and scallops were severely overcooked, and lamb loin baked in salt crust had lost its juices. It is a disillusioning evening when the highlights of a $75 dinner are a mushroom custard and broccoli florets that are garnishes to the main course. Even the souffle fell flat -- or, to be more accurate, was supported by far too much flour to allow its taste or texture to delight.

Last spring I had better luck, and with some of those very same dishes. This chef apparently can do it. His ideas are interesting, and twice in my experience he carried them out impressively. So for now, Fourways bears watching -- but dinner is an expensive gamble. 1701 20th St. NW. 483-3200. L $12.50-$15.50, D $21.50-$26. L daily ex Sat, D daily. AE, CB, DC, MC, V. Res req. Full bar.