Heat oil in large dutch oven over medium heat until hot. Add 1/4 of the beef cook turning frequently on all sides. Remove to plate. Repeat until all beef browned(not cooked through!)
Add onions and garlic to pan. Cook and stir over low heat until onions are soft and golden or 5-10 minutes. Add beef, beer, broth, parsley, bay leaves, vinegar, thyme, sugar, S&P to pan. Heat over medium to high heat to boiling. Then reduce heat. Simmer, covered, stirring occasionally, until beef is tender, about 1 1/4hrs.
Remove and discard parsley, bay leaves and surface fat. Add potatoes and carrots to pan; simmer, covered, 15 minutes. Add peas and mushrooms. Simmer uncovered, until potatoes and carrots are tender or about 10 minutes.
Mix flour and water in small bowl until smooth. Gradually stir into stew.
Cook and stir over medium low heat until thickened or about 3 minutes.