Best Answer - Chosen by the Asker
We'll break this into parts:
1) She's talking about how far she will have eaten into the bowl of ramen, if that makes sense. She starts with a full bowl, and begins to eat it. She will eventually have eaten half the bowl, and then almost all of the bowl of food. So, if she pushes the yolk to the bottom of the bowl while it's still full of noodles, she is saying that the hot noodles will continue to cook the egg yolk.
2) "Mostly," in that sentence, is referring to how cooked the yolk is. If it is mostly or nearly cooked, then it will be just a little liquid and raw still (it won't be FULLY cooked, if that makes sense). A raw yolk begins as entirely liquid. With her recipe, the yolk becomes MOSTLY solid. Think of it like the yolk of a hard boiled egg, but not as firm.
