In a large Dutch oven or stockpot, heat oil over medium heat. Add carrots, leeks and onion, and cook, stirring occasionally, until slightly softened, about 5 minutes. Add garlic and cook, stirring frequently, for 1 minute. Stir in mushrooms, salt and black pepper, cover, and cook, stirring a few times, until softened, about 10 minutes. Stir in potatoes and flour until well incorporated and cook for 1 minute. Stir in broth, scraping the sides and bottom of the pot to incorporate the flour mixture. Simmer until the stew just starts to boil, then stir, reduce heat to medium-low, and add orange rinds, prunes, thyme, rosemary and bay leaves. Let simmer, stirring occasionally and scraping the bottom of the pot, for 15 minutes, or until the potatoes are cooked through.
Stir in wine, tomato paste and soy sauce. Return to a simmer and cook, stirring occasionally and scraping the bottom of the pot, for at least another 15 minutes, until the stew is thick and the vegetables are soft (the longer it simmers, the thicker and more flavorful the stew will become). Before serving, remove orange peels, thyme sprigs, rosemary sprigs and bay leaves.