Black Bean Hummus

I have a not-so-secret love affair with hummus.  I have had a black bean version in my "to try" folder for forever, but I was lucky enough to try some at a local earth day celebration and promptly got the recipe.
1, 16 oz, can of black beans- drained, but reserve juices

1, 16 oz, can of black beans- drained, but reserve juices
1, 16 oz, can of garbanzo beans (aka chick peas)- drained
1/2 c. plain yogurt (I used sour cream)
1/4 c. lemon juice
1/4 c. extra virgin olive oil
1/2 head roasted garlic (I used about 8 cloves diced)
1/2 packet ranch dressing powder
2 tsp cumin

Blend all in a food processor.  Add reserved juices if needed to attain proper consistency.