Whatever I have on hand or fit’s the dish.

Mostly rapeseed oil, sometimes olive oil. When I first started (before I was able to just guess), I put a drop of water in the pan. As soon as the water started to boil, I added the oil and was ready to go.

Nothing stuck for quite a while. But if it did, sometimes it was enough to wait a bit for everything to release by itself.

Aside from that: butter. Butter does some magic.

And you don’t even have to use a cast iron. I’ve been cooking on stainless steel for a decade. I chuck it in the dishwasher when I’m done.

And as long as it’s oiled and hot, nothing sticks; not even eggs or fish. Especially if you use butter. But oil’s just fine.