In a skillet, heat oil over medium-high heat and brown pork chops on both sides; place in bottom of slow cooker when browned.
In same skillet, reduce heat to medium and saute onions until softened; add garlic, dry mustard, salt and pepper, and cayenne and cook, stirring, for 1 minute.
Add flour and cook, stirring, for 1 minute.
Add vinegar and wine and cook until thickened.
Pour this mixture over pork chops, put lid on crock pot and cook on Low for 4 to 5 hours or on High for 2 to 2-1/2 hours (I did Low for 4-1/2 hours), or just until pork is tender.
Remove pork chops from slow cooker and place on a warmed platter.
Stir Dijon mustard and whipping cream into juices in slow cooker; when well combined, turn slow cooker off and pour sauce over chops on platter and serve immediately.