Cream margarine, add brown sugar then egg yolk and vanilla. Mix well. Add flour and salt. Mix well. Batter will be stiff. Spread batter into lightly buttered large cookie sheet (with sides). Bake at 350 degrees for 20 minutes or until done. Melt chocolate in microwave according to package directions and spoon over hot cookie dough. Sprinkle with pecans and cut into squares when cool.