Irish Beef and Guinness Stew

Donal Skegan website:
https://donalskehan.com/

Ingredients for 4 large servings:
2 1/2 lb. beef chuck, cut in 2-inch pieces (tossed with black pepper and at least 1 tsp salt)
2 onions, chopped
1/2 tsp salt
4 cloves garlic, minced
1 can (14.0-oz) Guinness beer, or other dark beer
1/4 cup tomato paste
4 sprigs of fresh thyme
3 carrots, cut in 1-inch pieces
2 ribs celery, cut in 1-inch pieces
2 1/2 cups chicken stock, or as needed
1 tsp sugar
salt and freshly ground black pepper to taste