It may be the same one, LM, I got mine from an American website a few years back, can't remember what it was called now!
Here it is (imperial measurements, I'm afraid):
White vegetable fat (eg Trex) for greasing
8oz of marshmallows (recipe states white but I have used all pink when I wanted pink icing!)
0.5tsp clear vanilla flavouring (optional)
1 tbsp water
1lb icing sugar, sifted
Thickly grease a microwaveable bowl with the Trex
Put the marshmallows, water & flavouring (if using) into the bowl and microwave on High for 60 seconds (my m/w is a 1000kw beast of a thing so I did it for 20 secs at a time as I didn't want it to burn - took about 40 secs in total) or until the marshmallows have completely melted. Stir well in between bursts.
Put the icing sugar in a big bowl, fit a dough hook to your mixer (or use a wooden spoon but this will take forever!), pour in the liquefied marshmallow mixture and churn on a low speed until incorporated, then turn up the speed and allow the dough hook to knead the mixture until it all comes together and starts looking like proper fondant icing.
If still sticky, add more icing sugar as required.
Wrap in clingfilm and allow to cool before using. Roll out on a board and rolling pin greased with more Trex, as this will keep it lubricated, less likely to crack and if you're colouring it, you won't get those annoying streaks of icing sugar in the fondant when rolling/moulding either.
This makes TONS of icing, more than enough to cover a 10" cake (the original recipe specified double the quantities - I used it for the one on my profile that looks like 2 wrapped presents (a 10" and a 9" square cake plus trimmings but hadn't learnt the Trex trick then so it looks a bit 'dusty' with icing sugar), had enough left over to cover an 8" stacked cake afterwards and STILL had shedloads of the stuff!).
HTH
And if all else fails I thoroughly recommend Morrison's own brand of white icing - of the 4 I've tried (Asda, Sainsbos, Tescos) it is definitely the nicest tasting, softest and most malleable. The Tescos' own is hard like a brick and dries out as you look at it...