After a couple of years and a bit of refinement/experimentation, I decided it'd be worth reviewing my recipe for Fudge.
This is also a much nicer image for me to use, so...

Recipe (Vegetarian / Potential to be Vegan, as of yet untested)

125g Butter (Salted or Unsalted)
397g Condensed Milk
460g Sugar (used 300g Caster and 160g Light Soft Brown)
150ml Whole Milk

1 - Start by slowly melting the Butter in a large, thick-bottomed saucepan on medium heat.

2 - Add and whisk in the Condensed and Whole Milk. Allow the mixture to warm up a little before adding the sugar and stir until dissolved.

3. Once the sugar has dissolved, increase the heat to high and bring the mixture to a boil.

4. As soon as the mixture starts bubbling, spend the next ten minutes stirring gently (making sure you scrape the bottom regularly so the sugar doesn't burn*) and getting the mixture up to 115C (about 240F). The mixture should begin to look glossy. If you're after a firmer, crumbly kid of Fudge, I'd recommend boiling the mixture for an extra minute or two; otherwise stick with ten minutes to have your Fudge a bit soft and creamy.

5. Once the ten minutes have passed, remove from the heat and leave the mixture to cool down for about 10-15 minutes.

6. Use an electric hand whisk to beat the mixture into shape. This can take some time, but it will look matte and clearly feel thickened when you're done. This is usually the time where you'd add certain flavourings to the Fudge. A small amount of Rum or Espresso/Coffee, for example.

7. Spoon the mixture onto a parchment-lined tin or tray and smoothen the fudge out, then allow it to cool and set before removing and cutting it up.

Notes:
* With this particular batch, I put the mixture on high heat a little too early and ended up burning quite a bit of sugar at the bottom of the pan. This actually gave the Fudge a nice, almost rich bitterness which I didn't mind.
- It's important that you use a thick-bottomed pan and a sugar thermometer so you don't burn your mixture and you're able to keep an eye on the temperature.
- I'd also recommend using wooden utensils, with the exception of a metal whisk. Just no silicone, though, as they will melt under high temperatures.