I found the timing of this to be really important - down to the minute. The eggs might look like they aren't done if they are runny on top, but that can just be the cream rising to the top of the ramekin. If you cook these too long, the yolks get hard and they aren't as good.
Also, if you want the cheese to be melted on top, add the cheese before putting the ramekins in the oven. I didn't do this because it made it trickier to see if the eggs were done or not.