This is a rather lengthy recipe so I'm just going to post the link. I made this on Monday and really liked it! I discovered that there's not quite enough of the white sauce so you may want to make a bit more or just deal. I didn't mind it how it was but I knew Steven might think it was too dry (he was at school when I made it) so I bought some cheap Alfredo sauce and put a little bit on it for him and that seemed to do the trick!
Don't be afraid of the walnuts on top--they just give it a little crunch which is good! I've never done well with the texture of lasagna or especially ricotta cheese!
Anyway, it's delicious and a healthy alternative to regular lasagna!