Eggs – Mould in water when making preserved duck eggs

I ran across a good resource while looking into duck eggs. I'll let it speak for itself:

The higher protein in Duck Eggs means they mustn't be overcooked, or the whites will go tough and rubbery. Some people say they will be too tough if you completely fry them: they advise to rather partially fry them then add a few tablespoons of water to the pan, cover and let the steam moderate the heat and finish cooking them. Most people, though, seem to say they don't notice a difference between fried chicken and Duck Eggs.

Swapping Duck Eggs interchangeably in recipes for chicken eggs: some people say you can't; others who substitute all the time say nonsense, it's fine. When the Duck Egg whites are beaten they will come up a bit higher owing to the protein. They take a minute or so longer to start frothing up, but then make up for lost time.

There's a great deal more information on the page as well: http://www.practicallyedible.com/duck-eggs

No, it doesn't have to thicken, at least not in the way custards like creme caramel thicken. "Coat the back of the spoon" is just a misnomer, a term known to experienced cooks which confuses everybody who learns to cook on their own.

For "Coat the back of the spoon", read the comment riotburn left at the question What is the correct consistency of a cream soup?. It says: "The best way to describe 'coat the back of a spoon' is where if you dipped the spoon into the soup, take it out and holder over the pot, you'll find thin film (<1mm thick)."

For the ice cream, heat to between 80 and 85°C. I've explained it somewhere else, but in short, this gives you enough thickening without overcooking. If it is really gelato and not French style, it should be thickened with starch anyway. Also, watch videos on the Internet for how to make ice cream, they show the correct consistency. I think Allrecipes had a good one, but their search is so strange, I can't find it and don't know if they have it or not.