This appears to be fixed in the 1.101.290 patch.
@MaximumBlaze I've tested this on the stoves that are Functional Off the Grid and it works for me. My Sim has low cooking skill and he has eggs and bread in his inventory. He can cook Eggs and Toast on all of the stoves I have available to buy that work off the grid.
It does need to be a recipe though, so you couldn't just cook an egg it has to be an egg recipe. As long as the stove you have is Functional Off the Grid it should be fine for you. I click the stove rather than the fridge for off the grid cooking. It probably doesn't matter but that's just how I do it. If you have the Simple Living lot trait you'll need the additional ingredients too, either from the Grocery Delivery or grown/home made.
If it's not working for you still, drop us a reply and if you can it would help if you can take an image of it so we can see what you're seeing.
Hope this helps, good luck.
I'm pretty sure this used to work before the Cottage Living expansion, but it's been so long now I can't remember for sure. Now, if I use "Cook off the grid" on the stove, sure I can make eggs and toast. If I have the 2 eggs in my inventory, it will show Eggs (2/2) when I hover over the item. But it doesn't use the eggs when I try to cook them and it charges me the full amount. If I have enough power and use the normal cook option, it correctly uses the eggs and gives me the fresh ingredients discount. The only fresh ingredients the off-the-grid cooking option uses are the required items, not the optional ones (For example, if I cook popcorn crickets or fish on a stick, it uses up the cricket flour or fish).
The only way I've found to get off-the-grid cooking to actually use my ingredients is if I combine it with Simple Living... but then for some reason I need more fish for fish-on-a-stick? Once I have a couple of levels of fishing under my belt that's not so much an issue but when just starting out it can be a problem.
