Preheat the oven to 475°.
Put the shallots in a microwave-safe bowl. Microwave at HIGH for 1 minute.
Heat a small skillet over medium-low heat, add the bacon and cook gently, with the intent to preserve some nearly clear bacon fat. Separating the fat from the meat by melting the fat away is known as "rendering." cook until the bacon is crisp, but don't be so aggressive with the heat that you bring the fat to the smoking point. Spoon out the bacon and save it for garnishing later. Leave the fat in the pan.
Turn off the heat. Add the grapeseed oil to the fat in the pan. Swirl and keep warm.
Put the potatoes and the shallots in a large bowl. Pour in the bacon fat and oil mixture and toss to coat.
Place the potatoes and shallots on a roasting pan, and roast at 475° for 36 minutes or until tender and evenly browned, turning them every 10 minutes or so. Remove them from the oven.
Combine the malt vinegar, the brown sugar, and the salt in a small bowl until the sugar dissolves. Pour the sugar mixture onto the potato mixture and toss using a flat metal spatula.
Roast the vegetables 4 minutes more, until the sugar-vinegar mixture creates a slight glisten on the potatoes.
Transfer the vegetables to a serving bowl and toss with the parsley. Garnish with the reserved bacon. Serve.