Is there such a thing as Mezonos bread?
There is much controversy on the legitimacy of Mezonos "bread". Both Rabbi Pinchos Bodner and Rabbi Forst discuss this topic at length in their books (Halachos of Brochos and Laws of B'rachos, respectively). The latter seems to conclude along the lines of jutky's answer, but there are various qualifications that the ingredients of the bread must meet... CYLOR.
There's a great story involving R' Aharon Lichtenstein on an El-Al flight trying to get a permanent cup (which is a subject for another post) to wash his hands to eat his meal, which contained a "Mezonos roll". The flight attendant told him he didn't need to wash, and when he managed to obtain a cup and started washing, the same flight attendant adamantly insisted he really didn't need to wash and said, "If you don't believe me, ask a rabbi!"
With regards to mzonos in general, The Alter Rebbe writes in Hilchos Birckas Hanehenin (in the Siddur) it says:
1) If he eats less than 4 eggs and is full, wash on other bread.
2) If he eats less than 6 eggs, then if he is not full, one could say a mzonos. If he is full, he must say a bracha on this bread.
3) If he eats 6 eggs to half an Isarron, and he is not full, one must wash on other bread,
4) More than half an Issaron, one must wash on this bread alone.
The judgement of "is one full" on this bread includes condiment (like) the meat and eggs one eats with this bread.
Therefore, unless you eat less than 4 eggs, and you are not full from it, you gain nothing (and may have to wash on other bread).
6 eggs is around 12 ounces according to A"Ch Noeh.
Many Rabbanim don't like the idea of 'Mezonos bread' calling it a contradiction in terms.
Many quote the Da’as Torah (168:7) as allowing one to recite mezonos (and not having to wash and bentsch) even if one can’t taste the juice, providing that the main ingredient is juice, etc. R’ Yisroel Belsky points out that one can’t rely on this as he was referring to specific ingredients no longer used in baking.