Mix together flour, cocoa and salt in a bowl; set aside. In another bowl, blend together butter and sugars until creamy. Add 2 eggs, one at a time, beating well after each addition. Mix in vanilla. Gradually beat in flour mixture. Reserve ¾ cup batter, spread remaining batter into a greased 8-by-8-inch baking pan. Sprinkle pecans and white chocolate chips over batter. Drizzle caramel topping over top. Beat remaining egg into reserved batter until light in color, stir in chocolate chips. Spread evenly over caramel topping. Bake at 350 degrees for 30 to 35 minutes. Cool and cut into squares.