Well — yes, I mean I think the recipe would essentially work, though I think it’d be overly sweet for my tastes. You’re basically just adding a bunch of corn syrup to the recipe, that’s really all the filling in a creme egg is. Not to knock creme eggs, I love corn syrup and Cadbury Creme Eggs are my favourite, it just might get a little overwhelming in the recipe.
So you could do it, but I think it would actually be kind of a waste of a creme egg?
What I would do, actually, is still make it with nutella, but get some creme eggs, put them in the fridge to chill for a bit, and with a SUPER SHARP KNIFE cut them in half and then leave them out to warm up again (possibly with some plastic over them to keep the creme from getting weird).
Put half of an egg on top of the french toast when it’s fresh from the oven, chocolate-side-down (so that the creme isn’t touching the bread), press it into the bread lightly, and let it get a little gooey before you serve. That way you’ve got the aesthetic look of the creme egg, you retain the nutella slightly-less-sweet flavor, and people still get to eat half a creme egg. :D