Short expression for "If you are not 100% convinced yet, this last thing will seal the deal"

I'm writing a LinkedIn recommendation for a colleague of mine. I praised his abilities far and wide; now I would like to throw in one last (ironic and informal) punch line to top it all off.

Here is what I have so far:

You know how they say that if you want something done, you should ask the busiest person in the office to do it? This is the reason why Andrea is my favorite go-to guy for all of my data digging and reporting needs. Always working long hours, he still takes the time to patiently listen to me and assist me with whatever problem I have and, what’s more, he always does it with a smile. Quick, reliable and helpful, Andrea is also – and by far – the most polite and good-natured guy around. I am always at ease working with him.

Now I want to add something like:

What seals the deal? He keeps a huge stash of candies in the first drawer of his desk, for everyone to take.

Does that make any sense, or is the use of the expression "to seal the deal" inappropriate? What other choices do I have?

Please feel free to add any comment (also regarding the first part of the letter) if you wish.

I'd use "The icing on the cake? He keeps a huge stash of candies in the first drawer of his desk, for everyone to take."

Because it is a job recommendation, you might consider a little more formal way to introduce the candy story...

To sum it up, I'd like to add this personal anecdote. Andrea's generosity extends beyond his willingness to work long hours and help others. He also keeps a drawer full of candy that he shares with the entire staff! He's a sweet guy that will be a tremendous asset to your organization.