In the pan, melt 1-2 Tbl of butter and sweat the onions down. Deglaze the pan with malt vinegar, scrape the bottom of the pan and reduce until all of the liquid vanishes. Deglaze again with white wine. Pour in the creme fraiche. Pour the drippings from under the chops into the pan. Reduce the sauce, but do not reduce this sauce too severely. Creme fraiche is prone to breaking if pushed too far. Check for seasoning. Stir in the mustard. Turn off the flame. Return the chops to the pan. Turn the chops in the sauce. Serve over pasta.