Vegan Irish Stew

Name: Vegan Irish Stew
Cuisine: British, European
Ingredients: INGREDIENTS; 1 tbsp olive oil; 1 1/2 Cup Seitan Chunks; 1 large yellow onion, chopped; 4 cloves garlic, minced; 2 ribs celery, chopped; 1 carrot, chopped; 1 pound portobello mushrooms (about 18 small whole mushrooms); 1/4 cup tomato paste; 1 dark, stout beer (12-14oz can or bottle); 3 cups low sodium vegetable broth; 15 small potatoes; 2 bay leaves; 4 sprigs fresh thyme; 1 Tbs vegan worcestershire sauce; 1/2 tsp dried rosemary; 1/2 tsp salt; 1/4 tsp ground pepper; 2 Tbs corn starch or arrowroot powder; 1 Tbs water (to make a thickening slurry); fresh parsley for garnish