Fudgaster

While making my secret parcel for Snaterkat I decided to make some fudge. I know she has a liking for rum and raisin. I looked at several recipes on the internet and in books that I had. I eventually chose one (they were all pretty similar) and decided to have a go. I couldn't get hold of any condensed milk and so I also found a recipe for making condensed milk out of evapourated milk (basically adding a lot of sugar). I followed the instruction and poured out the fudge into a lined pan and after it had cooled a bit I stuck it in the fridge. The next morning I got up expecting it to be set, but it wasn't.

I admit I could have started all this a bit more in advance but I wasn't sure how it would keep and I didn't think I would have much trouble. I've made toffee and fudge before. So, I sent the parcel without the fudge, thinking I would be able to pass it on the next day. People at uni assured me it would take longer to set, but I'm sorry to say that it never has. So I decided to make a second batch. This time with condensed milk and adding the rum just before pouring it out into the tin. It worked a little better. The middle seemed to solidify quite quickly, but the edges never did.

I don't quite understand what I did wrong. I'm pretty sure I got it to a hot enough temperature (i.e. vigerously boiling for 10 plus minutes) and it looked like it was beginning to solidify just after I poured it, so what stopped it? Any useful advice would be helpful. Now I should go and make a start on using up some of this fudge sauce. ;)