Grate the potato and the onion together — the onion keeps the potato from going grey, which is why it is in the batter and not just for taste. Squeeze the liquid out, let the starch settle at the bottom of that bowl, and put the starch back in.
It did not make it into the plan for these seven days.
The method above is what decides the dish, not a step-by-step recipe. The link runs a web search on the name: this page has no vetted sources of its own, and will not invent any.