Gluten Free Chocolate Zucchini Cake

This time of year brings lots of zucchini.  I love zucchini and all the things you can do with it.  This recipe came from a family member and then I of course adjusted it to make it gluten free so I can enjoy it!!  This time around I did make an adjustment to make it a little healthier - but it still isn't the healthiest. It is still cake!! :)   It turned out great and with less fat and added protein.  I will note those differences in the recipe.

Ingredients:
1/2 cup       butter
1/2 cup       oil (I used 1/2 cup black beans that had been pureed - It will be a thick paste.)
1 3/4 cup    sugar
2                  eggs
2 cups         grated zucchini
2 1/2 cups  gluten free flour mix (I used 1 1/2 cups Featherlight + 1 cup GF mix +
                                                               1 tsp xanthan gum)
1 tsp             vanilla
1/2 cup        sour milk (1/2 cup milk + 1/2 tsp lemon juice)
1/4 cup        cocoa
1/4 tsp         cinnamon
1 tsp             salt
1 tsp             baking soda
1 tsp             baking powder
3/4 cup        brown sugar
3/4 cup        chocolate chips
3/4 cup        chopped nuts (optional - I used walnuts on half the cake because I like them but
                                                 the kids and hubby not so much)

Directions:
*     Combine all ingredients, except brown sugar, chocolate chips & nuts.  
*     Pour into 9 x 13 inch pan and sprinkle with brown sugar, chocolate chips & nuts.  
*     Bake in 350 degree oven for 40-45 minutes.