The phrase "again boiling" is correct and usable in written English.
It can be used when referring to a process or state of boiling that is happening once more after a previous instance.
Example: "After letting it cool, I placed the pot on the stove and watched as the water was again boiling."
Alternatives: "boiling once more" or "boiling again".
At the Israeli-Lebanese border, perhaps precipitated by Hezbollah's desire for distraction away from Assad, tensions are again boiling over.
The moment was not easy, coming at a time when tensions between Jews and Arabs are once again boiling into violence a thousand miles away in the Gaza Strip and the West Bank.
Ronaldo was presented with his second consecutive Ballon d'Or a couple of days later but his team then tumbled out of the Copa del Rey against rivals Atletico Madrid, and the forward was soon held to another blank in a poor performance at Cordoba, with his irritation again boiling over as he earned a straight red card for a petulant hack at opposing defender Edimar.
Add the desired amount of spaghetti, gently stir continuously to keep it from sticking, until the water is again boiling.
This again boils down to compromise.
Much of the reason, I must emphasize again, boils down to bad luck.
Nearly a half-century later, the controversy again boils down to a he said/he said situation.
To qualify as a genuine hot dog, the crescent must be smoked or boiled or in some way precooked before it is again boiled or grilled or fried or baked or nuked.
1937 Labor Conflicts Intensify NEW YORK — The labor stew in Mid-Western industrial centers again boiled over today [June 5] as workers and officials exchanged words and missiles in several points where the conflicts are the hottest.
Despite Lewis Hamilton's switching to Mercedes, Vettel still wins a fourth straight Formula One driver's title in the final season of the V8 engine, and it once again boils down to the final race in São Paulo.
That also suggested that life might have arisen several separate times, since the next giant meteor impact would have again boiled off the oceans and killed any organisms on the planet.
