2 tablespoons chopped fresh flat-leaf parsley, plus more for garnish
2. Add onion, carrots, and celery to the drippings in the pot; cook, stirring often, until the vegetables begin to soften, about 4 minutes. Add tomato paste; cook, stirring constantly, for 1 minute. Add beer and thyme; cook, scraping the bottom of the pot to release any browned bits, until the liquid is slightly reduced, about 2 minutes. Add broth and the beef (with any accumulated juices in the bowl); bring the mixture to a boil over medium-high heat. Reduce heat to medium-low; cover and cook until the beef is mostly tender, about 1 hour, 10 minutes. Stir in potatoes; cover and cook until the beef and potatoes are tender, 15 to 20 minutes.
3. Whisk cornstarch and cold water in a small bowl. Increase heat to high; add the cornstarch mixture and cook, stirring constantly, until thickened, about 2 minutes. Remove from heat; stir in parsley. If desired, garnish with additional parsley.
To make ahead: Refrigerate the stew in an airtight container for up to three days or freeze it for up to six months. Thaw (if frozen) and reheat before serving, either on the stovetop or in the microwave.
Recipe nutrition per serving: 405 Calories, Total Fat: 12 g, Saturated Fat: 3 g, Cholesterol: 102 mg, Carbohydrates: 32 g, Fiber: 4 g, Total Sugars: 4 g, Protein: 37 g, Sodium: 704 mg, Potassium: 904 mg, Iron: 4 mg, Folate: 39 mcg, Calcium: 50 mg, Vitamin A: 5347 IU, Vitamin C: 14 mg.