This recipe (the first one -- scroll down) by Hugh Fearnley-Whittingstall is essentially an eggs Florentine, but with kale rather than spinach. The difference is that you mix the green vegetable with the cheese sauce, rather than pouring the sauce on top.
One way of making eggs Florentine is to prepare the spinach and the sauce, put the spinach into an oven dish, crack the eggs on top, pour over the sauce, and bake for about 20 minute. The problem is that it's hard to tell whether you are overcooking or undercooking the eggs. Or you can prepare the spinach and put it into a dish, poach the eggs to your desired consistency, rest them on the spinach, pour on the sauce, and flash the dish under a grill. This time the problem is that it's easiest to prepare the spinach first -- but then how do you keep it warm? In a low oven, perhaps. Fearnley-Whittingstall's technique seemed worth a try.
Never again. After 10 minutes, both the egg yolks and whites were runny. Arriving at set whites and soft but not runny yolks took 25 minutes, by which time some of the white was hard and adhering to the sides of the dish. The washing up was a pain.
In this entry, I described a hybrid between the two methods mentioned above. It now seems to me to be best to put the spinach in a warm dish in a warm oven while you poach the eggs and allow your bechamel to simmer. Put the poached eggs on to the spinach, stir the cheese into the sauce (it need only be melted, rather than cooked), pour the sauce on top, and place under the grill (I put the dish into the grill pan with the rack removed) until bubbling.