Basically, it's fudge with caffeine...quite a bit of caffeine to be precise. Caffeine has been identified many, many times to be a performance enhancing drug, albeit a legal one. Cyclists love it, and I had several, all independently, ask if I was going to make a caffeinated version, as I had done with my flapjack.
It's actually pretty easy to bake with caffeine powder...it's stable to a pretty high temperature, way above anything you'd bake at. The only downside is that it is very, very bitter. The flapjack was sweet, and also had some strong, long-lasting flavours in cherry and chocolate, so there was no issue. the vanilla fudge I've made has a pretty short-term flavour (it sort of melts in your mouth, and is then gone), and it turns out that the caffeine bitterness does outlast it. It's not terrible, and it seems like it fades as the fudge fully sets, however I'm thinking next time I'll flavour the fudge, probably with cocoa.
The actual method is pretty simple...I did exactly the same as last time, and added exactly 1g of 100% caffeine powder (the maximum temperature the mixture reaches is 116'C, so no danger of breaking down the caffeine) right at the start. It goes without saying that you have to weigh the caffeine very carefully (and don't breathe it in). I was aiming for a dosage of about 200-250mg per portion. I worked this out by weighing the final slab (470g), then chopping it up into small pieces (I quartered it, and then chopped each quarter into 8 pieces). I have some small ziploc bags, and it turned out I could fit 6 pieces in each bag...this worked out at 90g/bag for 5 bags, with a couple of bits left.
A bit more maths, and this comes to 192mg of caffeine in each bag...that's a pretty big kick (for reference, an SIS double-expresso caffeine gel is 150mg). Their maximum dosage is two per day (I agree with that, I once took two on a hot day, and passed out with two laps of a race left). There is also just over 400 calories in the fudge as well, which will keep you going for 25-30 minutes at full tilt.
So I bagged it up, whipped up some basic labels, and handed it out to a couple of guinea pigs for a Saturday race. The flavour, as mentioned above, is slightly compromised, but I can work with that. I certainly had "good legs", though my positioning still sucks...one other lad did really well. It's now a few hours after the race, and I still feel completely awake, which doesn't bode well for tonight (the Insomnia flapjack is well named...caffeine is a great stimulant, but it can ruin your sleeping patterns). Even worse, there are 2 more bags in the fridge...