It depends on what you know: do you know how big the portion is 20 minutes before it arrives? do you know whether you will like it and eat all of it? do you know how long you will be waiting between courses?
If you are not nervous about injecting, I would split the doses. I usually
- once the order has been taken, start with a smallish dose to cope with the minimum carbs I would expect in the first course and any correction dose if my current BG is high.
- when I have finished my first course, I would have a top up injection to cover the actual carbs I have eaten and my minimum expectation from my second course.
- when I have finished my second course, I would have a top up to cover anything I missed.
This probably sounds like quite a faff but
- it allows for the insulin to start working before you eat
- takes into consideration what you have actually eaten (you don't have to force yourself to continue eating something you don't like because you have taken the insulin)
- allows for the kitchen and waiting staff to take their time (and you and your fellow diners to have a relaxing meal)
- you do not have to take a BG reading before every injection (only the first)
- to make it quicker, I arm my pen with a needle before I go out and don't change it during the evening (yes, I know this is naughty but saves me looking for a sharps bin)
If you are drinking with your meal, don't forget to take this into consideration and don't forget to take a BG reading before you go to bed. And don't worry if you were slightly out - you don't go out very often so you should enjoy it.