Chocolate Zucchini Cake

One of my mom's recipes (and a great way to use up garden zucchini):

Ingredients:
1/2 cup butter, softened
1/2 cup soil
1-3/4 cup sugar
2 eggs
4 Tbl coca
1/2 cup buttermilk
1 tsp. vanilla extract
2-1/2 cups flour
1/2 tsp. baking soda
1/2 tsp salt
1 cup walnuts, chopped (plus extra for the top)
2 cups zucchini, chopped fine (unpeeled)
chocolate chips (for the top)

Preheat oven to 325 degrees.

Grease and flour 9x13 inch pan and set aside.

Cream butter, oil and sugar.

Beat in eggs, cocoa, buttermilk and vanilla and set aside.

In a separate bowl, sift together flour, baking powder, baking soda, salt; add the first mixture and mix well.

Stir in 1 cup chopped walnuts and zucchini.

Pour into prepared pan. Sprinkle with chocolate chips and chopped walnuts. (sometimes I've used white chocolate chips)

Bake for 45 minutes or until toothpick inserted in the center comes out clean.