Step 1

Place potatoes in a large saucepan with enough water to cover by 1 inch. Bring to a boil. Adjust heat to maintain a lively simmer and cook until tender, about 30 minutes. Drain and return to the pan. Add milk, butter, ½ teaspoon salt and ¼ teaspoon pepper. Mash to desired consistency. Cover to keep warm.

Step 2

Meanwhile, heat oil in a large skillet over medium-high heat. Add beef and cook, breaking into large chunks and flipping occasionally, until browned on all sides, about 6 minutes. Sprinkle with the remaining ¼ teaspoon pepper. Transfer to a clean plate.

Step 3

Add mushrooms, onion and garlic to the pan and cook, stirring occasionally, until just starting to brown, 5 to 8 minutes. Sprinkle with flour and the remaining ¼ teaspoon salt and cook, stirring frequently, for 1 minute. Return the beef to the pan and stir in beer, broth and Worcestershire, scraping up any browned bits. Bring to a gentle simmer. Cover and cook until the beef and vegetables are very tender, about 20 minutes. Add peas and carrots, increase heat to medium and cook, stirring occasionally, until the stew is slightly thickened, about 5 minutes. Serve with the mashed potatoes, sprinkled with parsley, if desired.