In a mixing bowl beat butter until light and fluffy. Beat in brown sugar and vanilla. Blend in flour. Pat mixture evenly into bottom and half way up sides of lightly buttered 15-1/2 x 10-1/2 x 1-1/2 inches jelly roll pan. Bake in preheated 350-degree oven 15 minutes. In a saucepan combine condensed milk, butter, vanilla and salt. Heat over low heat, stirring occasionally until butter is melted and mixture boils and thickens. Stir in 1 cup chopped peanuts. Pour mixture into baked crust in pan. Bake in preheated 350-degree oven 15 minutes, or until lightly browned and set. Sprinkle chocolate bits over top. Let stand until bits are soft enough to spread evenly over top. Sprinkle top with 1 cup chopped roasted peanuts. Cut 12 x 16. May be frozen. Makes 72 bars.