There are two things which are referred to as Malt in breadmaking--either
diastatic malt powder (available from KA Flour) or barley malt syrup, which
you can get at most health-food stores. Both are simple sugars which are
derived from malting (or sprouting) barley, and they not only contribute
sweetness--though much less than table sugar--but they also promote enzyme
activity and add to the leavening effects of yeast. I've used both, and
lean towards the barley malt syrup, as it's a less refined product. You
only use a couple of tablespoonfuls in a recipe, but it will keep
indefinitely in your fridge. A tip when measuring it: spray the cup or
spoon with vegetable oil spray (such as Pam(R)) before pouring it in, and
it will come out very nicely, it's extremely thick and sticky.
Susannah