Yesterday, I took the cut away desem and made desem dosas. I had never made dosas with desem that was so young before, it but it still came out great.
Dosas are thin unleavened South Indian bread made traditionally from fermented rice and something called "black gram". Epicurious.com says that gram flour, or besem  is chickpea flour...but no chickpea I know of is black...so I'm not quite sure what "black gram" is. [Edit: I stand corrected. Apparently beige is not the only color of chickpeas! See comments from Alberto .] Here  is a recipe for real dosas. I haven't found black gram anywhere here in Zürich, but in the meantime the dosas made from excess desem is mighty tasty. The added benefit of desem dosas is that you're using something that you might have to throw away anyway (extra desem), so you get to feel smugly frugal too. I almost make desem just for the sake of being able to make these dosas. They are that good. And, they are so easy to make.
Desem dosas are more sour than desem breads because you let it ferment at room temperature for 3 hours or more. Actually, it tastes better when it's pretty sour. It makes a great accompaniment for curry and other spicy dishes, or even with the Breakfast fry-up with spicy potatoes , instead of having toast. (It then becomes more of a lunch than a breakfast.) It's also great used like Norwegian lefse (flat bread made with rye flour), and eaten with smoked salmon or other smoked fish, sour cream, cream cheese etc. But my absolute favorite way of eating it is with plain cottage cheese and a drizzle of honey. It's also pretty tasty just on its own, especially if you cook it until it's crispy.
Note: the book  gives a recipe for desem dosas, but it's curiously incomplete - for example, it doesn't say how much desem you need. Well I have the previous edition, so maybe this has been corrected in the current edition. Anyway these are the proportions I use.
Dissolve the desem in the water. Younger desem will have stringy gluten in it, but mature desem will disintegrate completely in the water.
Add the flour and mix well. Cover the bowl and let it stand at room temperature for at least 3 hours. You can also leave it for a day or so in the refrigerator, but you should let it stand at room temperature for at least an hour before cooking.
When it comes time to cook it, it may have separated, so mix it well, and add a bit more water or flour to make it into a thickish batter, about the consistency of pancake batter. At this point you can add a bit of salt if you like, though I find that the tanginess of the desem makes this unnecessary.
Heat up a non-stick frying pan. (You can make it in a regular frying pan but it will probably stick unless you add copious amounts of oil.) Heat until a drop of water sizzles in the pan, then add some oil. Add the batter. Spread it around with the back of a spoon or something, and cook until the bottom is cooked and a bit crispy. Turn over and cook briefly on the other side. It's best if the dough is firm enough to turn over comfortably. Like crepes, for some reason the first dosa comes out rather badly, but subsequent ones come out fine.
Eat while warm. If you need to reheat them you can do so in the microwave, or briefly in a frying pan.