Divide the udon into 4 portions. Chop up the chives into 3 cm pieces. Wash the bean sprouts and drain well.
Put everything in Step 1, the ground meat and the egg into a bowl and mix well. Add enough flour to hold everything together, and season with salt and pepper
Spread some oil around in a frying pan or on an electric griddle, spread the mixture around thinly and fry. When both sides are nicely browned, serve with ponzu sauce and ra-yu if you like it.
You can omit the bean sprouts if you'd prefer. If you do use them, increase the amount of flour a bit in order to hold everything together. I've gotten comments that this tends to fall apart, so please take note of this: When you're pan-frying it, cook it as you would prepare okonomiyaki - slowly and patiently.