I just bought some ready made puddings and added three drops of green dye. I put a chocolate gold coin at the bottom and then plopped the pudding on top. I added whipped cream and gold sprinkles. If you are worried about the foil touching the pudding (frankly, this is probably the least of our problems, but...) you can wrap it in syran wrap and then put it in the bottom of the cup.
I adapted this poem from the same site. Here is a free printable.