IMAGINE the London Master Chefs Association talking about David Brown. ''Nice chap,'' they would say. ''Wonder what became of him?'' ''Took off to the Orient, I hear. Decent chef he was; won some awards, then vanished to a remote island.'' Wonder no longer. For their information, David Brown is alive and thriving in his kitchen kingdom on Peng Chau island. The master chef, who's had a successful career on three continents, is happily married, happily employed, and has the kind of work which most chefs would only dream about. ''I cook the way I want to cook,'' Brown said, carefully pouring out a soupcon of marjoram into his Italian tomato soup. ''I don't see any competition on Peng Chau for my kind of food.'' With a fraction of the usual Hongkong expenses he can experiment with Spanish tapas without worrying about the Yuppie crowd complaining. Brown makes certain that what you order one day will never be the same the next day. You don't like the mussels stuffed with beef? ''All right, I'll change it next time,'' he said. ''Instead of bechamel sauce, I'll put in sauce provencale. That should suit you.'' Until this month Brown hardly had a menu at all. The little board outside the restaurant used to list the dishes - always some Spanish specials (Brown won an award from Hongkong's Spanish Consulate for his food), chicken , steaks, lamb chops, his choice of pizzas - easily the most delicious on any island - and a cheesecake to die for. Now Brown has succumbed to popular demand and actually has a menu. Canneloni and lasagne, grilled garoupa, mushrooms with Chablis sauce, peach melba . . . not exactly the kind of food you usually find on this dot of an island, so tiny you can encircle it in a few hours. Fishing is still the main industry, and Brown's restaurant fronts on the picturesque harbour. Once fairly rustic, today the houses seem to be built on top of each other. But the little lanes breathe southern Chinese atmosphere of the last century with porcelain factories (far cheaper than in Hongkong), a few steel-pounding garages and boats anchored off the jetty where you can buy live fish to bring back to Hongkong. Brown has been working in his own kitchen kingdom since he started cooking in England. A native of Scarborough he answered an advert and started in the Amsterdam Hilton kitchens. Then he worked through Switzerland and Germany, down to South Africa's President Hotel and finally to Hongkong. While he tried to avoid the hotel chef syndrome, he did become involved with the better private restaurants. He was involved with the Stanley Group, as they expanded along the seashore. He plunged ahead with Duddell's, worked at Casablanca and became executive chef with the Zanussi Corporation. His job there was as a chef's chef, demonstrating Zanussi kitchen equipment to chefs throughout Asia. ''This is the kind of job where the sales manager tells the chef that Zanussi can do anything. My job was to sigh, and explain to chefs professionally what the equipment could and couldn't actually do.'' But Brown's goal was taking him out of the rat race. In November, Brown bought into Sea Breeze and now has what few other chefs have - a carte blanche to run things any way he wants. Brown serves up more than food. This March he plans a Spanish weekend, including feasts, boats and - for the first time on Peng Chau - a troupe of Flamenco dancers. Maybe it isn't the dream of every chef to have their own kitchen kingdom in the sun. But for David Brown, peering over his soup, this is simmer-time. And the livin' is easy. Sea Breeze Restaurant, 38 Wing Hing Street, Peng Chau, Open: Noon to 11:30 pm; closed Monday, tel: 983-8785.