Adjust oven rack to bottom position and preheat oven to 275℉ (135℃).

Trim off any large and hard fat pieces from chuck roast, then cut into 1 ½-inch pieces. Pat dry with paper towels and sprinkle all over with ¾ teaspoon salt and ½ teaspoon black pepper.

Heat olive oil or duck fat in a large heavy-bottomed pot or Dutch oven over medium-high heat until shimmering. Cook half of beef until browned on all sides, 4 to 5 minutes. Adjust heat to avoid burning. Transfer the browned beef to a plate, then repeat with remaining beef.

Reduce heat to medium and add the bacon to the pot with the rendered beef fat. Cook, stirring frequently, until just starting to brown, about 4 minutes. Add the onions, carrots, and parsnips, and cook, stirring frequently, until the vegetables start to soften, about 3 minutes, adjusting heat as needed to avoid scorching the vegetables. Sprinkle vegetables with remaining ½ teaspoon salt and ¼ teaspoon black pepper.

Add the garlic and flour and cook, stirring frequently, until fragrant and no dry flour remains, about 1 minute. Remove pot from heat, add the brandy, stir, then return to heat and cook for 1 minute.

Slowly whisk in wine, stock or broth, thyme, and prunes. Bring the mixture to a simmer over medium-high heat and simmer until slightly thickened, about 5 minutes. Add the beef and juices from the plate to the pot. Cover and transfer to the oven. Cook until the beef is fork tender, 2 ½ to 3 hours.

Remove stew from oven. If necessary, place over a burner and simmer uncovered, stirring occasionally, for up to 20 minutes to reduce and thicken stew to desired consistency. Use a ladle to skim excess liquid fat from top of stew and serve right away, garnished with parsley. Or—for the best tasting stew—omit skimming step, cool stew, and reserve for the next day. To serve the next day, let stew rest at room temperature until no longer hot, about 1 hour, then cover and refrigerate overnight. When ready to serve, spoon off hardened fat from the top and reheat stew on stovetop over medium heat until hot, about 15 minutes. Garnish with parsley before serving.