Interestingly I have only ever used or heard used definition #2 below. Definition #1 seems alien to me.I think it also takes more than one dish to justify the use of regale, which heavily implies lots of something.
What exactly do you believe that "lush" means? The usage you are showing is very atypical. Perhaps we can advise you on the meaning once we understand what you believe "lush" means.You mean a lush dish means it's only one plate?
Maybe this version is better?
It's Manfredo's birthday today, therefore he has regaled his friends with several lush delicacies.