Butter an 8 x 4 inch (19 x 9 cm) pan or dish. Yes, a bread pan will do fine.
Measure butter and the cheese into a deep pot, and melt the butter over gentle heat, whisking it in. Then whisk the sugar in, and stir occasionally as the entire mixture melts and start to bubble. (Mind the bubbling sugar. It can "plop" upwards and give a nasty burn, as it sticks to your skin while burning you.)
After about 5 minutes, do the "soft ball" test. That's when you drop from a teaspoon a bit of the mixture into some cold water in a clear drinking glass or measuring cup. If it dissolves into the water, keep on cooking. If it holds its shape, you're ready for the next step.
Turn off heat, move to a burner that wasn't on, stir in the vanilla. Now you go crazy with the whisking. Whisk the blazes out of it until you feel it getting really heavy (if you have a whimpy arm, don't try telling us it's heavy after 30 seconds) and it is starting to visibly thicken. At that point, stop -- any further mixing would make it go grainy.
If you are going to add any optional ingredients, fold them in now.
Pour into the buttered pan and let set to harden (will take about an hour.)
You may find it easier to cut it into pieces before it gets completely hard. You can still leave the pieces in the dish to finish hardening, just get them cut.
All fudge is a bit of futzing.Even though a wooden spoon feels more traditional, use a whisk: it's way more efficient and your arm will thank you.At the initial stage, though, as the ingredients are starting to melt into each other, don't mix too much. Occasionally means occasionally, or your fudge will end up grainy.If you can get golden caster or granulated sugar, the unrefined crystals would add an additional rich taste to the fudge.You can add optional ingredients such as nuts or raisins. The dried cranberries look fabulous and their tangy taste is a good foil to the sweetness.