boil down (Verb) — Be the essential element. ex. "The proposal boils down to a compromise"
boil down (Verb) — (cooking) be cooked until very little liquid is left. ex. "The sauce should boil down to one cup"
boil down (Verb) — (cooking) cook until very little liquid is left. ex. "The cook boiled down the sauce by boiling it for a long time"