I wouldn't even bother cooking them...just crush them and add them to the mix! Great idea and I will try it also. Usually I just feed them the shells directly, crushed and placed back into the layer mash but since I'm fermenting layer mash for the layers when they come, I'll just throw the shells right in there. That's why I love these forums...every once in awhile you can get a good exchange of ideas going that really enrich the whole learning process when it comes to raising your own foods. So..the vinegar mix doesn't harm the plants at all? You'd think it would make the soil a little acid, wouldn't you? I already crush egg shells and place them in the same hole as I plant the tomatoes but I never thought of soaking in vinegar first....thanks for the great tip!!!