Here is the egg tempera recipe I use when I make it for my paintings. It’s the one I learned from my teacher, Brigid Marlin and I love it.
2 tbs titanium white pigment powder
2 tbs medium:
Mix 1 whole egg, half eggshell of linseed oil and half eggshell of damar varnish.

You want to get a sandblasted glass surface as well as a high quality muller.

This lasts in the fridge for 3 weeks and I’ve definitely kept it for longer myself but it is best to use immediately and make smaller batches like this to keep it fresh. I would not recommend making in bulk as a little goes a long way.

Let me know if you try it and what you think.