Cork?? That's only good for plugging bottles. 30 years of replacing cork gaskets has left a bad taste. Only the cheap after market still uses cork.
In nearly any situation, if you have a smooth surface and a good gasket, sealer will add another layer to fail. It's required in corners where gaskets end or join others, but there is NO reason to use both on a flat surface.
Put a layer of silicone on a cork gasket. Tighten it down. See the sides pooching out? That's the gasket splitting as the silicone adds lubrication to the cork allowing it to split even easier as the pressure of tightening it makes it want to squeeze out the sides.