Apple Crumb Bars

In a bowl, combine brown sugar, oats, flour, baking soda and 1 cup plus 2 tablespoons butter. Reserve 2 cups for topping; lightly pat remaining crumbs into a greased 13-in. x 9-in. x 2-in. baking pan. Arrange apples on top of crumbs; set aside. In a saucepan, combine sugar, cornstarch, water, vanilla and remaining butter. Bring to a boil and cook until thick; spread on apples. Sprinkle reserved crumbs on top. Bake at 350 degrees F for 35-45 minutes or until top is lightly browned. ');