Cooking is not always easy for overly logical people. It requires a qualitative approach- knowing when something is "done" is an art, not a science. Unfortunately I only want to work with numbers and I'd imagine a lot of my fellow maths students are the same- following the instructions on the back of packets to the letter (and usually being disappointed with the results or the need to compromise between two wildly different cooking temperatures for the two halves of a meal). Given that potatoes don't have instructions on the packet- or indeed, a packet- I humbly present here the first in a possible series of Cookery for Mathematics Students nodes- the humble roast potato. I've tried to make the instructions clear enough for me to follow, which should render them essentially idiot proof.
Select 2 potatoes per person, assuming that each person wants 4 roast potatoes and 2 potatoes are of sufficient size to meet this demand- they usually are.
Peel the potatoes. I can offer no useful tips here, as I have the most slow, lethal and blatantly cack-handed approach imaginable. This is because I am left-handed, whereas my mother (who attempted to teach me) is right-handed and slices towards herself anyway. Slicing towards your wrists is a bad idea but I can't find an alternative approach. Slice the peeled potatoes in half to get the desired number and a flat surface that will sit more easily on the tray.
Wash the potatoes using cold tap water, then transfer to a saucepan which should then be filled with enough water to just submerge the potatoes- too much and it'll take longer to boil (i.e. cost more) and too little will cause what's above the water to turn an interesting brown colour. At this point it's perfectly acceptable to leave the pan of potatoes to sit there, so if you're doing a complicated meal and need several things ready at about the same time, you may find it convenient to prepare the potatoes this far in advance of starting to cook.
About an hour and a quarter before you want to eat, proceed to the following steps.
Firstly, bring the pan of potatoes to the boil. This will require the lid to be on the saucepan and the hob to be on maximum power. Once the water has boiled (trust me, you'll know), reduce the temperature to about half the maximum (you can tell my gas ring doesn't have numbers, just pictures of flames) and leave for about 5 to 8 minutes more. Whilst you're waiting, add some vegetable/sunflower oil to a baking tray and warm this in the oven to 180oC - if you don't have a fan assisted oven, you might have to wait 15 minutes or so to hit this temperature so plan ahead. Gas or fan-assisted should get there in time.
Then remove the pan from the heat and turn the hob off so you don't accidently set yourself on fire when you turn around to the sink. Turn around to the sink, and drain as much of the water out as you can without losing the potatoes in the process- the lid will come in handy here. Then place the saucepan on the kitchen side and shake it vigorously in a horizontal motion. This will make the potatoes a bit fluffier and hence crispier when they are finished. If you don't like your roast potatoes resembling a crispy fractal, then you can miss this step- but I'd recommend it.
Now transfer the potatoes to the baking tray of hot oil. As the name suggests, hot oil is indeed hot and is generally nasty stuff. Don't get it on you, especially if you cut yourself using my suicidal peeling techniques earlier. Baste the potatoes by spooning some of the hot oil over the top of them- if you don't have a deep enough level of oil, tip the tray slightly so you can collect it. Generally you want a deep tray so that you'll find it harder to slosh the oil over yourself.
From here it will take about an hour for the potatoes to cook at 180oC. At 15 minute intervals baste them with oil again, and at the mid point turn the potatoes over entirely.
Once done, place a couple of pieces of kitchen towel on a plate such that the edges overhang, and transfer the potatoes onto the plate. Loop the overhanging edges of towel over the top and press down on the potatoes (lightly- this isn't mash we're making) and blot the oil off of the potatoes. Then transfer to the plates you're actually going to eat off (in this way, more washing up can be generated) and enjoy.
As a final note, the oil you used can be reused within the next couple of days. If you won't be doing this (or if you did and it's now a few days old), you've got to dispose of it (fairly obviously). Whilst some people don't advocate it, you can get rid of oil down the sink, but the oil should be cold and flushed down with a vast excess of boiling water (from a kettle- hot tap water is not sufficient in either volume or temperature). Alternatively, if you have such a thing, you can just chuck it in the garden. I make no guarantees that either process is acceptable, legal or hazard-free where you live, so proceed with caution, or as a true student of initiative, leave it for someone else to deal with.