Bring broth to a boil and add the potatoes. After it boils again, add milk.
Meanwhile, to make olive oil with aciote seeds, you heat the oil in a small frying pan with 2-3 achiote seeds over med heat until the oil turns an orange color. Do not let the seeds burn, as the oil will taste bad.
Saute the onion in the colored oil until translucent.
When potatoes are almost done, add the onion.
Separate the egg. Beat the yolk and add some hot soup to it, mix and add it into the pot. Stir well. Beat the egg white a little and add into the soup. Stir with a fork, Ribbons will form.
Add in the cheese and stir until melted.
Add salt and pepper to taste. You can sprinkle sliced green onion tops or cilantro on top to serve.
As kids, we put a scoop of rice in the bowl and poured the soup onto it to serve. Delicious!