Hoosier Bars

Yields 3 dozen.

1 1/2 cups all-purpose flour
1 teaspoon baking soda
1 cup packed brown sugar, divided
1/2 cup granulated sugar
1/2 cup (1 stick) butter or margarine, softened
2 large eggs, separated
1 teaspoon vanilla extract
2 cups (12 ounce package) NESTL? TOLL HOUSE