These are somewhere between a cake and a brownie. Not a SUPER fudgy brownie, but not a cakey one either. Moist and delicious - not to mention healthy!
A regular blender will probably work for this, you just might need to run for longer. I have a Vitamix(R) and it took about 2 minutes total to blend everything. If using a food processor or other unmarked container, pour the zucchini puree into a 4-cup (or larger) measuring cup and then add prunes until the puree reaches the 3-cup mark. Then dump it all back in the processor and blitz away. You want the zucchini/prune/chocolate mixture to be smooth before you pour it onto the flour.
Feel free to use pecans in place of walnuts.