For the suet pastry, in a large bowl, mix together the flour, suet, salt and chopped parsley.
Gradually add the water in a thin stream, stirring continuously with a fork, until the mixture comes together as a dough. (NB: You may not need to use all of the water.)
Turn the dough out onto a lightly floured work surface and knead lightly for 1-2 minutes. Wrap the dough in cling film and chill in the fridge for 15-20 minutes.
Meanwhile, for the filling, heat the oil in a pan over a medium heat. Add the shallots and chopped garlic and fry for 8-10 minutes, or until softened.
Add the thyme leaves, mushroom ketchup and Irish stout. Continue to cook for 2-3 minutes, stirring well.
Add the stock and mushrooms and bring the mixture to a simmer. Continue to simmer for 10-12 minutes, or until the volume of liquid has reduced slightly and the filling mixture has thickened. Season, to taste, with salt and freshly ground black pepper. Set aside to cool slightly.
Once the pastry has chilled, divide it into four equal pieces
Pinch off a quarter of the first portion of pastry and set aside to use as the pudding lid. Roll out the remaining pastry portion onto a lightly floured work surface until it forms a circle large enough to line one of the pudding basins.
Carefully lift the pastry using a rolling pin and line the pudding basin with it. Allow any excess pastry to hang over the sides of the basin.
Spoon a quarter of the filling mixture into the pudding basin.
Roll out the reserved pastry lid onto a lightly floured work surface until it is slightly larger in diameter than the pudding basin.
Brush the rim of the lined pudding basin with water. Cover the pudding with the pastry lid and press the edges of the pastry together to seal. Trim away any excess pastry, then cover the exposed lid of the pudding with a double sheet of aluminium foil, pleated in the middle to allow room for expansion as the pudding cooks.
Repeat the process with the remaining three portions of pastry, the remaining filling and the remaining pudding basins.
Prepare a steamer pan, then steam the puddings in the pan for 40-45 minutes, or until cooked through.
When the puddings are cooked through, carefully remove them from the steamer pan using oven gloves. Set aside.
When the pudding basins are cool enough to handle, unwrap the top of the puddings. Remove the foil from each pudding basin. Invert one pudding onto each of four serving plates.
Serve immediately with steamed courgettes and carrots.