Chef Mavro   George “Chef Mavro” Mavrothalassitis' food is in a category of its own. He's part of the Hawaii Regional Cuisine crew, but what comes out of his kitchen bears little resemblance to what his peers cook. The ethnic Greek from Marseilles extracts the essence of a food, then enhances it, so that for example a hint of star anise on a delivered-that-day, perfectly poached Keahole lobster sings in your mouth of spice and sea. Regulars won't let Mavrothalassitis take his roasted lamb loin off the menu; it's just so sinfully tender and the flavor heightened by, say, spiced green olives and a confit of North Shore-grown tomatoes. The clinical technique and ingredients on each plate speak of hours of research and work on the part of Mavrothalassitis and chef de cuisine Kevin Chong. For the wine pairings on the quarterly-changing menu, manager Todd Ashline ferrets out several selections, then the staff gathers for a lengthy day's tasting, voting for the best matches. There are four prix-fixe menus 3, 4, 6 or 11 courses (a quarter portion of everything on the menu).  1669 S. King St. 944-4714. 6-9:30 p.m. Tuesdays-Sundays. Reservations recommended. Valet and self-parking. AX, DC, DS, JCB, MC,VS. Checks accepted. $$$.  Web site: www.chefmavro.com