I can't remember exact proportions, but for 1 okonomiyaki, I usually
use 2-3 cups cabbage (whatever fits into a donburi bowl), 1" of a 2-3"
diameter yamaimo, grated, 1 egg, about 1/2 tsp of dashi powder, and 1
heaping Chinese soup spoon (the ceramic kind) of flour. I usually mix
the egg and dashi together so the dashi gets a little better dispersed
when mixed into everything. Then I add that and the yamaimo to the
cabage and mix. I add the flour last. My friend's mother (who taught
me how to make okonomiyaki--mine is Osaka-style) said the "batter"
should be like an earlobe. It's pretty thick, but not like pancake
batter usually is. But it's quite soft. And the wet ingredients just
sort of coat the cabbage--there shouldn't be a lot of batter in the
bowl.

If I can, I'll take pictures and post to eGullet, then link here to
it. There's a whole topic there on okonomiyaki with lots of different
variations. But...I still like mine best. :-)