milk (light cream) is used in baked products to give moisture, sometimes
flavor, and color (it'll make baked things a kind of more golden color).
buttermilk is often called for in recipes and this is to provide a different kind
of flavor and also sometimes to serve as the acid that activates the baking soda
in the recipe so your thing will rise.
as with this butter stuff, well, butter is often called for instead of margarine probably
because of some dairy industry plot that bought off all cookbook manufacturers and made them
print "butter". there's no problem with substituting margarine one for one (make sure there's
no whey in it.) BUT, don't substitute products labeled "spreads" for butter or margarine cuz
they've got a completely different fat make-up/content, and you won't end up with the same
baked thing that you had really hoped you would. kay?
finally we've got these slimy egg things that can sometimes give me a really big headache when i'm looking
for good substitutes. eggs are used in recipes for any number of reasons. one big one that i've finally
figured out is that they're sometimes just used because tradition dictates so. you know, it's not a real
cake unless you've got some eggs in it. bullshit! forget it. sometimes you can leave out the eggs and add
no substitute and your baked thing works out just fine.
the three main reasons eggs are in baked things tho is to add liquid to the recipe and keep things moist,
to leaven the baked goods (make 'em rise), and to bind the ingredients together so your brownie doesn't just
turn out a pile of crumbs. now, replacing the liquid of an egg in a recipe is easy -- you can just substitute
about 2 1/2 tablespoons of any kind of liquid for each egg the recipe calls for. keeping the products moist is
another story tho, and i've found very few great vegan cakes that have that same moist texture as the old egg-y
cakes had. one way you can do it (and in this case, ignore the 2 1/2 tablespoons bit) is by substituting 1/2 a
mashed banana or 1/4 cup applesauce or other fruit puree per egg. of course, a slight banana or apple flavor
in your chocolate cake may seem a bit weird though. the best one i've found is blending about two ounces of
mashed tofu with the liquid in the recipe for each egg called for. tofu really doesn't have much flavor and i
think does the best job of moisturizing.