In a buttered 2-quart saucepan, combine sugar, corn syrup and water. Cook
and stir over medium heat until mixture comes to boiling. Continue cooking,
without stirring, until mixture reaches the hard-ball stage, or until candy
thermometer registers 260 degrees F. Remove saucepan from heat.
Meanwhile, in large mixer bowl, beat egg whites, at medium speed of electric
mixer until stiff peaks form.
Gradually pour hot syrup over egg whites, beating constantly at high speed
Add vanilla extract; beat for 4 to 5 minutes until candy holds its shape.
On towel dusted generously with confectioners' sugar, quickly pat candy
into a 10 x 4-inch rectangle. Dust quickly with more confectioners' sugar.
Using a rolling pin dusted with confectioners' sugar, roll candy to a 16
x 6-inch rectangle. Spread Jif over candy to within 1/2-inch of the long sides.
Roll up from opposite side, using towel to help roll.
Wrap in towel; chill.
To serve, cut into slices slightly less than 1/2-inch thick.