I purchased a 8.8 oz jar of Pommery Moutarde Royale. It is the one in a ceramic(?) jar that is corked and with a wax seal. I've removed all the wax around the mouth of the jar, only some wax is still left on the cork top. I have run a small knife around the tight space between cork and jar, but can't seem to get the cork to move at all. Am I suppose to use a cork screw? This is quite an expensive jar of mustard and I am trying to not butcher the cork into bits into the mustard. Thanks any experienced advice with opening this product is appreciated.