Something interesting about proverbs is that for every proverb that exists, there's often another one which means the exact opposite. The opposite of this one is: 'Many hands make light work.' This suggests that the more people there are doing a job, the easier it will be! The other thing to remember about proverbs is that while we do use them in everyday conversation, we almost never say the full expression. Everyone knows these sayings, so there's no point in saying the whole thing. So, if we can see that there are too many us trying to help with a simple job and it seems to be going wrong, somebody will mutter 'Hmm, too many cooks...' and everyone will understand.

It means too many people giving their opinions on something/being involved in making decisions on something can lead to a bad outcome. If there are 10 people all cooking something it might turn out bad. Sometimes, you just need one person making the decisions. According to Google, the Italian version is: Troppi cuochi guastano la cucina.