Preheat oven to 325 degrees. Mix, with a spoon, all ingredients, just until blended. Pour in ungreased 9-by-13-inch pan. Spread batter evenly. Bake for 40 minutes, until golden brown. Spread on sour cream topping, and then sprinkle with another cup of coarsely chopped walnuts.
For topping: Mix in a three-quart pan topping ingredients.
Slowly, on medium heat, while stirring, bring mixture to a boil. Let
boil for one minute. Spread on cake while both are still hot.