Once you have chosen your country, start with a reliable source to build some background knowledge about customs and tradidtions. This is how you can gather specific search terms for more in-depth searching.
An encyclopedia is a great place to start for this kind of information.
Now that you have specific foods and holidays to search, you can use a search engine to find more information about those items.
For example: I might search Chile holiday food or, if I know the name of a specific holiday, I can search Chile Christmas food.
Other food-related words you might try:
When searching the internet, you'll come across a variety of websites. A quick look at the site's URL can be your first hint about whether or not a site is reliable. What you may find: