Preheat oven to 350 degrees. In a large bowl, beat cake mix, oil and egg on medium speed until crumbly. Add nuts. (If cake mixture forms large lumps that stick together, mix a little longer after adding nuts and then break up lumps with a fork - you want it crumbly like large pieces of streusel.) Reserve 1 1/2 °C of crumb mixture and press the remainder firmly on the bottom of a greased 9x13 pan. In a small saucepan or microwave safe dish, combine condensed milk, chocolate chips, vanilla and salt. Over medium heat, cook and stir until chips melt (about 1 min. In microwave). Pour evenly over prepared crust. Top with reserved crumb mixture. Bake 25-30 min. Or until surface looks slightly bubbly. Cool and cut into bars. Store loosely covered at room temperature.