A few years ago, when I was a teenager, I had a book called Picture Chords for Guitar. The book taught chord shapes for example an F - and showed how this same shape could become a G or an A simply by moving the shape up the neck of the guitar. Once you had mastered a chord shape you could use it over and over again to make new chords on different frets. The book never taught me to be a great guitarist, but the idea of a shape that could be used more than once was an attractive one. It occurred to me again recently while I was trying out a new pasta sauce.

If you can make a white sauce, then you can make a bechamel, a cheese sauce or any derivative of the same shape. If you can make mayonnaise, then you can make a sauce aurore or an aioli. Master the basic shape, and the others follow as easily as sliding your fingers up and down a guitar neck. Just as variations on a theme is standard procedure in music, it is also the secret to innovative cooking. I think of it as 101 Chord Shapes for the Kitchen.

One of my favourite pasta sauces is pesto. It's named after the way it's made - that is in a mortar and pestle. This is still the best way to make it; a liquidizer is faster, but the taste changes - I think because the speed of the chop heats the basil. The principle is simple: grind fresh basil with a mortar and pestle, adding as you go olive oil, grated Parmesan, garlic and optionally pine-nuts until your sauce is thick and rich. It keeps well in a fridge for a week or two, so you can make more than you need for one meal and put the rest into a jar for a quick snack another time. I don't really approve, but you can bulk out the sauce with parsley if basil is scarce.

This principle of making a sauce with a mortar and pestle is a good one, and there is no reason why basil should be the only herb so used. It is a theme as variable as any other. You can make an unusual pasta sauce this way using rocket instead of basil. As ever, use good olive oil, freshly ground Parmesan rather than pre-packaged and less garlic than you would for pesto. It's not the purist way, but in the spirit of adventure you could try thyme, rosemary or oregano - I haven't yet, but I intend to experiment.