In a large bowl, cream shortening, 1/2 cup of brown sugar and sugar until light and fluffy. Beat in egg yolks. Combine water and vanilla. Combine the flour, baking soda and salt; add to creamed mixture alternately with water mixture, beating well after each addition.
Spread in a greased 15x10x1-in. baking pan. Sprinkle with chocolate chips. In a small bowl, beat egg whites over medium speed until soft peaks form. Beat in remaining brown sugar, 2 tablespoons at a time, on high until stiff peaks form. Spread over chocolate chips. Top with peanuts. Bake at 350° for 30-35 minutes or until set. Cool on a wire rack.