[lukan]

Well Wikipedia says there is a narrow definition, that necessarily involves boiling of a liquid. This is the one I always used.

But in the broader sense, it seems to also mean the preparing of meals, but I never encountered it like this.

"Kochen (von lateinisch coquere, „kochen, sieden, reifen“ entlehnt) ist im engeren Sinne das Erhitzen einer Flüssigkeit bis zum und am Siedepunkt, im Weiteren das Garen oder Zubereiten von Lebensmitteln allgemein"

"es kocht" literally means, it is boiling.

[kragen]

the cognate 'cook' in english also has a broad meaning (preparing food) and a narrow one (heating food to induce chemical change) but even the narrow one is not so narrow as to require boiling water

the problem with 'cooking bread' is that 'baking bread' is a set phrase, not that baking doesn't count as cooking

[account42]

Der Koch darf auch braten.

The wider meaning is pretty common in German to the point I find it hard to believe any native speaker wouldn't ever have used "kochen" to refer to something other than literally boiling water.