Mix the flour, suet, salt, and parsley in a large bowl.
Stir in water until the mixture forms a dough.
Knead the dough for 2 minutes, wrap in film, and chill for 20 minutes.
Fry chopped shallots and garlic in oil for 10 minutes.
Stir in thyme, mushroom ketchup, and stout for 3 minutes.
Add stock and mushrooms, then simmer for 12 minutes until thickened and season.
Divide the chilled pastry into four equal portions.
Remove a quarter of one portion for the lid and roll the rest into a circle.
Line a 300ml pudding basin with the pastry circle.
Fill the basin with a quarter of the mushroom mixture.
Roll out the reserved lid portion slightly larger than the basin.
Brush the rim with water, seal with the lid, and cover with pleated foil.
Repeat the assembly process for the remaining three basins.
Steam the puddings in a steamer for 45 minutes.
Remove the basins from the steamer carefully.
Unwrap the foil and invert each pudding onto a plate.
Serve immediately with steamed vegetables.