Ok so Goodfellas is my favourite Gangster film of all time and my second favourite Scorsese motion picture. Without getting too in depth about this genius scene, I'll just summarize using already known analysis, comments on this video and some of my own interpretation.

• Song by the Crystals is in Karen's mind and tells the audience what she's feeling
• Henry and Karen go through the back entrance, skipping the queue to get ahead-this reflects on Gangster lives: how they can get everything in life but have to go through the 'back' entrance to do it, that is, getting their hands dirty
• When the guy opens the door he represents a demon or satan and looking at the blood red walls and floor we can see that the foyer represents hell
• Henry greets everyone and is familiar with them---this is to impress Karen. From her perspective this is a man who brushed her off once but is now taking her through the back of an exclusive dining place, giving people wads of cash in the 70/80s no less which, adjusting for inflation would be...well I'm shit at maths so lets just say it's a lot
• Some of the people they walk past are wearing black/red to further emphasize hell
• They get a table right at the front
• The long, unbroken take works to show fluidity and make the scene more palpable

So on this first date Karen is thinking: this guy is rich, this guy is important, this guy is a rat so cool