Cooking For Engineers

[chopchophands]

Ok so I have a couple of questions.
First, I've been looking at gnocchi recipes and I'm wondering if gnocchi is supposed to be coming out like a pasta/potato(ish) dumpling or more of a potato tasting dumpling. Also, are eggs necessary? Whole or otherwise?
Second, I'm a little confused on the whole subject of demi. I know that a demi is supposed to be heavily reduced stock, down to a syrupy consistency, but I know restaurants sometimes use espangole. How would espangole be substituted for demi? And what qualifies as a demi?

Thanks.