Fat Fish serves up fresh seafood, applying French culinary techniques to Japanese cooking in a hip, West Hollywood atmosphere. Our chefs give an Eastern tinge to traditionaly Western cuisine, adding soy and ginger to steak and potatoes, and select fine wines, sakes and champagnes to accompany your meal.   The Scene Dark-wood furniture, deep-red banquettes and Zen-inspired paintings create a stylish dining room for laid-back locals and fashionably casual couples. Out on the patio, diners watch the parade of barhoppers head to the nearest hot spots. Servers are attitude-free and quick to rattle off favorite menu items. The Food The seafood-heavy menu pairs Eastern spices and sauces with traditional Western ingredients. A favorite is the tuna trio appetizer, which features a mound of spicy toro, chunks of peppered albacore and silky ahi sashimi neatly arranged on a plate. Fat sushi rolls made with non-traditional combinations like raw scallops and fried tempura crisps are filling. Other entrees include flaky black cod topped with a wild mushroom crust, served with mashed potatoes in a pool of yellow curry. Desserts range from a decadent banana split to soothing green-tea ice cream.