Ready, Steady, Teach!

What's the fastest you've ever put a lesson together from scratch? And no, I don't mean just turning to pages 42-48 in Headway Intermediate. How long do you think it takes?
Watching the execrable wasteland that is daytime TV in the UK, one of teh brighter moments was 'Ready, Steady, Cook' on BBC2. For those who don't know it, the idea is that two cooks have to make several dishes from a bag of ingredients given to them by members of the studio audience. Of course, they also have a fridge and larder stuffed with the basics, but it requires imagination.
So why not do it ourselves when it comes to lesson prep? I think it is possible to create a one and a half hour lesson, from scratch, in about 20 minutes. Here are the rules:
1) there are clear aims and objectives to the lesson.
2) you are allowed to use any 'off-the-shelf' ingredients, but you cannot use more than one page from a standard textbook and nothing directly from a workbook
3) there must be at least two skills practised, one as a main focus, one as subsidiary - so, for example, listening and speaking/pronunciation
4) there must be at least one original piece of work - this can be an adaptation of 'off-the shelf' materials or techniques, or an entirely new piece.
5) you get extra points for the relevant use of realia or current new items.

Sure, this is what we're meant to be doing, but in reality, I think we either overplan (if we're beginners, or doing a Dip.) or we just reach for the safety and convenience of a textbook. The latter is all very well and fine - after all, they're the product of people with years of classroom experience - but they are designed with an idealised, generic class in mind. Without wanting to be rude, they are McLessons - the pedagogical equivalent of fast food. When we know our students and their needs, it is clearly not enough to give them this fare all the time.