Preheat oven to 400°F. Generously brush madeline pan* with melted butter; dust with flour. Combine eggs and next 4 ingredients in bowl of electric mixer. Set over saucepan of simmering water and stir until lukewarm. Remove from over water and beat until pale yellow and tripled in volume. Add vanilla. On low speed gradually mix in flour, scraping bowl occasionally. Transfer 1/3 of batter to medium bowl. Gradually fold 3/4 cup melted butter into batter in medium bowl (do not fold in water at bottom of butter). Return to remaining batter and gently fold in. Transfer batter to glass measuring cup. Pour into madeline molds, filling almost to top. Bake until cookies are golden brown and springy to touch, turning pan halfway through cooking, about 12 minutes. Invert pan onto rack. Gently pry out cookies with knife tip. Sprinkle with sugar. Wipe out molds, grease with melted butter, dust with flour and repeat with remaining batter. Cool. Store airtight. *A metal mold with scallop shell shaped indentations, available al specially cookware stores. A mold that makes 12 cookies is available for $23.25 from A Cooks Wares, 3270 37th St., Beaver Falls, PA 150 10; (412) 846-9490. cook 035