The breakfast had to be in a local cafe of course. Croissant and a cup of coffee will do.
We found a nice cafe with artistic atmosphere and beautiful paintings in the local area - Latin Quarter.
The price of course is a bit of a shock in the beginning (in this one coffee was 3,70 euro and croissant was 1,60), but you just have to accept - you're in Paris . That's why you pay more.