Is there a mold I can pour egg white into to create an egg white only hard boiled egg? If not, is there some other way to accomplish this?
Are you starting with whole eggs or just egg whites? I ask because it’s easy to hard boil a whole egg and then just remove the yolk from the whites when you are finished.
Blow out one of the eggs you’re getting the whites from and use that as a mold.
What I want to make is a whole hard boiled egg made from egg whites, not just remove the yolk from a hard boiled egg.
1.That method gives us a mess of white and yolk mixed together.
2. Even if you could separate the white from the yolk in that mixture, how do you get the white back into the egg through those tiny holes?
I’m just gonna say. No. You can’t get the yolk out cleanly. With out breaking the egg.
If you have collected enough egg whites over a day(I wouldn’t keep them longer than that)
I’m very sure there are silicon egg shaped molds that are cooking safe. Like the silicon muffin molds.
Send pix when this works. 
Does it have to be egg shaped? If not, just poor 3 tbsp of egg white into a plastic baggy, cinch it up tight, and boil.
You’re worrying whether you could. Stop and ask if you should.
Yes, it has to be egg-shaped.
I found one that makes chocolate eggs, but they’re hollow. I can’t find any molds that would seem to work. Maybe do the blow-the-egg-out trick with a bigger hole, and use a funnel to get just egg whites back in there?
Get one of those plastic eggs that hold candy. Fill the halves with raw egg white and submerse them partially in boiling water. Use a little more egg white as glue and put the halves together and finish cooking.
Also, search on “long eggs” for some other information about cooking egg white in molds.
What do I plug the big hole with?
I think @TriPolar’s method is probably the way to go, but maybe you could tape it up, although I don’t know what kind of tape can handle being boiled for many minutes.
Boiling water will warp the plastic egg and it will come apart, and reusing an already boiled egg doesn’t seem to be a solution so far either.
That’s tricky. Cooking a liquid medium into a perfectly oval shape is going to be all but impossible since the whites won’t expand to fill the vessel.
If you do a search for silicone “egg bite” molds you’ll find lots of shapes, some of which are egg-like, but I can’t imagine how you’d get an actual egg without some kind of injection device for filling a mold.
You can get molds for ice balls. I have some they work, well not so well. Kinda bad design.
I’ve been thinkin’ on it a long time and there’s no easy way to make ice balls in a stand alone mold. It’s long drawn out drivel as to why it doesn’t work. Don’t buy one. Worthless.
I’m assuming the the egg shaped molds available would be just as hard to use. Plus they have to be cooking safe.
So, I’m still going with “No”. Can’t be done easily.
I think those make hollow eggs…or maybe not. Hard to tell.
That’s pretty good, though, definitely trending in the right direction. It would have an ugly dent at one end but even regular hard boiled eggs are imperfect.