1) Place potatoes and garlic in a medium saucepan and pour over enough water to cover. Set the pan over a high heat and bring to the boil. Cook for 8 minutes, until the potatoes are fork-tender. Drain and return the potatoes to the pan with the garlic to pan.
2) Add the sour cream and mash until almost smooth (or lumpy if desired). Stir in parsley and season, to taste, with salt and black pepper.
3) Meanwhile, heat the oil in a large frying pan over a medium-high heat. Season the pork chops with salt and black pepper and add to the hot pan. Cook 2 minutes per side, until golden brown. Remove the pork from the pan and set aside.
4) To the same pan, add the shallots and cook 2 minutes, until soft. Add the thyme and tarragon and cook for 1 minute, until fragrant. Add the sparkling wine and cook for 1 minute.
5) Whisk the flour into the milk and add to the pan. Return the pork chops to the pan and simmer for 3 to 5 minutes, until the pork is cooked through and the sauce thickens.
6) Serve the pork chops with the sauce on the mashed potatoes.