Preheat the oven to 180°C.
Fry chopped onions and mushrooms in oil in a large casserole dish for five minutes.
Coat cubed beef in a mixture of flour, salt, herbs, and pepper.
Add the beef and flour to the onions and fry for 5 minutes.
Stir in bay leaf, stout, stock, tomato purée, and sugar, then bring to a boil.
Cover and cook in the oven for 135 minutes until the beef is tender.
Reserve 450ml of sauce for gravy and simmer the remaining mixture until thickened.
Remove the bay leaf and allow the meat mixture to cool completely.
Mix flour, suet, parsley, salt, and water to form a soft dough.
Divide the dough into four portions weighing 100g, 150g, 200g, and 275g.
Layer the pastry discs and beef mixture into a buttered 1.5 litre basin.
Cover with pleated parchment and foil, tying securely with string.
Steam the basin in a pot with water reaching halfway up the sides for 120 minutes.
Let the pudding stand for five minutes before inverting onto a plate.
Serve in wedges with the reheated reserved gravy.