The recipe I've used for years came from the Nestle site, that link is gone now it seems, but here's the same recipe Rainbow Cookies (Thought I'd link it as recipes have copyright as well).
The recipe now uses caster sugar instead of regular sugar, but otherwise it's the same.
And as a hint, if you want your cookies looking like the ones in their photo, instead of mixing in the Smarties, you need to flatten each cookie and push in the Smarties by hand, yes that's what I did too.
I admit I haven't made Smartie Cookies for ages, instead I use a similar recipe (you can use this one) and I put in a bag of choc chips and 1/2 a cup of chopped up white chocolate to make Triple Chocolate Cookies - a little more grown up.
A bag of regular or Peanut M&Ms instead is also a yum alternative, as are Rum soaked raisins for Chocolate Rum & Raisin Cookies..
The real reason for dragging out the recipe this time was THESE
They're fairly new on the market, so I just had to give them a try!
There's a recipe on the back of the pack as well, but I thought I'd give them a whirl in the Chocolate Cookie Recipe. I used the whole pack, other than a few we taste tested first :-).
They don't go gooey soft, but keep their shape when cooked and gave the cookies a subtle caramel flavour with the chocolate, so give them a try - Jen.