Sift flour before measuring. Mix water, cornstarch, eggs, sugar and vanilla together. Stir slowly into flour, then beat until smooth with rotary beater or electric beater at medium speed.
Prepare the batter. Add approximately 2" oil in a deep fryer or sauce pan. Heat to 365 F.
Attach rosette mold to handle. Immerse mold into the hot oil until thoroughly heated. Lift mold out, shake excess oil or blot on paper towel.
Dip mold into batter, BUT ONLY until it covers 3/4 up the side on the mold. IMPORTANT! Do NOT cover entire mold with batter.
Dip the mold-battered into the hot oil. As soon as the rosette begin to turn golden, lift the mold, and let the rosette drop into the hot oil.
Sprinkle with powdered sugar to taste, or use or cinnamon and granulated or brown sugar, or fill with your favorite garnishment.