"Vi spiser kokkenes mat."

Indeed it is, and that's also our recommended translation which is shown up top.

If you have issues with the plural possessive being graded incorrectly for this sentence and/or being shown a possessive without the required apostrophe as a recommended answer, please take a screenshot and make a thread about it in the Troubleshooting forum and/or report it as a bug.

Remember to make it clear that this is a recurring issue affecting all plural possessives, and not just a case of a missing accepted translation.

We made the developers aware of this issue over a year ago, but new features keep getting priority over bug fixes. Perhaps a little more user attention in channels they actually read might do the trick.

Because "kokkene" already means the cooks (definite plural), so adding possessive-S makes it the food that belongs collectively to the many cooks.

If it was just the cook's (definite singular) food, that would be "kokkens mat".

Refining your English grammar rules while learning foreign languages, it always happens! ;)

"Cook's" indicates a thing or things that belong to one cook. "Cooks'" indicate a thing or things that belong to two or more cooks. Using an apostrophe between the K and the S indicates a singular cook. Using an apostrophe after the S always indicates plural cooks. Example #1: "Those are the cook's books." (This indicates one cook and two or more books.) Example #2: "That is the cooks' book." (This indicates a singular book that belongs to two or more cooks.) (Also, pay your cooks more so that they can all afford their own books.)

"Cook's" can also indicate a contraction. Example #3: "The cook's reading his book." This has the exact same meaning as: "The cook is reading his book." It would only be used with a singular cook.