I actually made a Molecular Gastronomy recipe today that I was quite proud of. It's Agar Agar Tomato Soup Spaghetti, invented by Ferran Adría of El Bulli.
There are two essential bits of kit needed for this recipe - a big chunky syringe, and lengths of plastic tubing. The tubing has to fit very tightly over the nozzle of the syringe, otherwise all your efforts are doomed to failure. After quite an extensive search, I found tubing of the right size (about 4mm internal diameter) in the gardening department of El Corte Inglés - it's intended to be part of an irrigation system.
So, here's what you do. Make some tomato soup (or even open a can if you're not that bothered about what it tastes like). When ready, whizz it in a blender and then strain through a tamis or bit of cheesecloth. Return to the heat and add about 5g of powdered agar agar. Remove from heat when the agar agar has dissolved.
Now the fun part. Cut a length of tubing about 2 metres long. Coil it up a bit and secure the coil with a couple of bits of sticky tape (you don't have to do this, but it makes things easier later in the process). Fill your syringe with tomato soup - you'll need about 45ml to fill your 2m tube. Fit one end of the tubing over the syringe nozzle, and carefully inject the soup into the tubing. When a bit comes out of the other end, you're done. Remove the tube from the nozzle and pop it into a bowl of iced water. If you intend to make more than one spaghetto, repeat this paragraph.
Now the magic part. Agar agar is a gelling agent, and it sets at room temperature. Once the soup and agar mix has set in the tubing, fill your syringe with air, attach the tubing, and press the plunger on the syringe. You don't want to use too much force at this stage because once the frictional resistance of the spaghetto has been overcome it will emerge pretty fast and you need to avoid it hitting walls, ceilings, floors, cats or houseplants.
You can dribble your spaghetto randomly on a plate, or arrange it in an arty-farty spiral, although they are a little delicate and prone to breaking. You can serve the spaghetti cold or warm them over a pan of boiling water - be careful though, because they will melt at about 70°C.
And you can make them from virtually any liquid you fancy, as long as it's smooth enough to be injected into the tube. I think my next attempt will be with gazpacho.
Oh, and the reason I was proud of this is that the tutorials I'd read warned about the difficulty of using the syringe to extract the spaghetto, and recommended a nitrous oxide cream whipper to blow it out, but I suspect this was because they didn't have a tight-enough fit between their tubing and syringe nozzle. Or maybe they just like playing with laughing gas.