There's a "too broad" close reason, for sure. And when voting to close, people sometimes to say "poll" questions are bad, and often mention something about "one correct answer" - what's the deal with all of this? What sorts of questions are and aren't okay?
It's fine, and often even good if a question can have multiple good answers. There is no rule that questions have to have a single correct answer.
Many problems in the kitchen can have multiple good solutions, and we want people to ask about real problems, and learn what we can about various ways to solve them. All of that knowledge is useful to collect together.
However, we want to avoid questions with too many good answers, and that's exactly what the “too broad” close reason is for:
There are either too many possible answers, or good answers would be too long for this format.
Note that there a few things that matter here:
- sheer number of potential answers - it's bad if there are literally just too many possible answers (whether already posted or not yet)
- difficulty of voting - it's also bad if no one can reasonably judge which answers are good
- is it a real problem? - solving a specific problem constrains number of answers and eases voting, while requests for general knowledge can be dicey
With too many answers, it's hard to read them all, and voting tends to turn into a popularity contest: quick, obvious answers well, while later or less-popular suggestions do poorly. On top of that, duplicate answers become common. All of this gets even worse if it's hard to judge how to vote. The already sketchy voting gets even more random and even more based on instinct and popularity.
A really extreme example of "too broad": What cookbooks do you always come back to? has 86 answers, and some of the classics are up at the top, but beyond that it's pretty much chaos. Since the criteria are so general, and no one's read all those books, it's hard to even expect voting beyond popularity.
On the other hand, What methods make tomato chopping less messy? clearly has multiple possible answers, but is perfectly fine.
What to do
In the end, this is just about figuring out where to draw the line: how many is too many? If a question can easily have 10 or 100 different good answers, that's a recipe for trouble. If it's likely to only have a handful of really good answers, and there's a decent way to tell which ones those are, then it's probably just fine.
Between those extremes, we just have to use our best judgment. We don't want to end up with 100-answer disasters, but we also don't want to close questions that realistically only have a handful of good possible answers. When in doubt, we should err on the side of not closing; we can always deal with it if something turns out to have more answers than we imagined.
Especially if you have close-vote privileges, some general things to keep in mind:
- edit questions to avoid broadness
- request clarification to avoid broadness
- vote to close when warranted - we need everyone's help as usual
- explain what "too broad" means - the language in the close reason is very helpful for this!
- say "questions should have a single correct answer" - no, they don't have to, and telling people this makes our rules sound way too strict.
- say "there's more than one correct answer, so this is a poll" - no, a poll it's just a popularity contest, and not all multiple-answer questions are like that
- vote to close for those reasons
Further hypothetical examples
- Bad: What are your favorite frequently-used cookbooks? (tons of options, no criteria to judge)
- Probably fine: What's a thorough cookbook for authentic Oaxacan food, in English? (not many published)
- Knife skills
- Bad: Resources for knife skills (huge scope, room for debate on details)
- Good: What's a good generic mincing technique, with videos? (still has wiggle room, but specific enough to fit in a question)
- How to cut something
- Bad: What are some fun ways to cut potatoes to roast? (tons of options, no clear winners)
- Good: What's the best way to cut cheesecake into bite-sized portions? (not many options)