First the beans need to soak and, to do this, either put them in a large saucepan with 4 pints (2.

25 litres) of cold water and bring them up to the boil for 10 minutes, then turn the heat off and leave them to soak for a minimum of 2 hours, or else soak them in cold water overnight.

To make the casserole, heat 2 tablespoons of the oil in a large frying pan, then wipe the pieces of oxtail with kitchen paper and coat them lightly in seasoned flour and fry in hot fat on all sides until they are a nutty brown colour.

Then, using a slotted spoon, transfer the pieces of oxtail to a casserole.

Now add the rest of the oil and, as soon as that's hot, add the onions and fry these for about 5 minutes until brown at the edges, before transferring them to join the oxtail in the casserole.

Remove the pan from the heat, then drain the beans in a colander.

Add them to the casserole along with the garlic cloves, sprigs of thyme and bay leaves and add a good seasoning of black pepper.

Next wipe the open cap mushrooms with some damp kitchen paper, halve them (or quarter them if they are very large), then add these to the casserole as well, tucking them in among the beans and oxtail.

Now return the pan to the heat, add any remaining seasoned flour, stir it in to soak up the juices and gradually add the stock and the Guinness, whisking all the time until it reaches simmering point.

Pour it over the oxtail and the rest of the ingredients, cover with a tight-fitting lid and place in the pre-heated oven for 2¬Ω hours.

Then add the chestnut mushrooms halved and wiped as above, put the lid back on and give the casserole a further hour in the oven.

When you next remove it, you will see that some of the fat from the oxtail has bubbled up to the top – spoon this off by skimming a tablespoon across the surface.

Then season everything well with salt before serving with a lightly cooked green vegetable.