Mini Kiss Blondie Bars

1/2 cup butter or margarine, melted
1/2 cup shortening
1 cup packed light brown sugar
1/2 cup granulated sugar
2 eggs
1 teaspoon vanilla extract
1/2 teaspoon baking soda
2 1/2 cups all-purpose flour
1 3/4 cups (10 ounce package) Hershey