Hi Pelin, No, I don't think we use them interchangeably. It’s cooked well. Means the quality is good. Tastes good. Prepared correctly. Not about the inside being fully cooked. It’s cooked thoroughly. Means it is fully cooked all the way through. No raw parts. This is about doneness, not taste or quality. If you mean the food is delicious and perfectly prepared, you should use "cooked well." If you mean the food is safe and the center is not raw, you should use "cooked thoroughly." Hope this helps!

One note is that some restaurants (at least in the US) will use "well" as an option when you order steak or something similar. For example, "would you like your steak well, medium well, or rare?" So in this specific context, "cooked well" could mean 'completely cooked.'

B