How to make the best Irish bacon, cabbage and parsley sauce for St Patrick's Day

Darina Allen's bacon and cabbage with parsley sauce is hard to beat.
For many of us, bacon and cabbage is our national dish making it the perfect dinner for St Patrick's Day. The original Irish one-pot meal, Darina Allen says that it was down to necessity rather than ease.
"Traditionally, the cabbage was always cooked in the bacon water. People could only hang one pot over the fire at a time, so when the bacon was almost cooked, they added the cabbage for the last half hour or 45 minutes of cooking.
The bacon water gives a salty, unforgettable flavour, which many people, including me, still hanker for. You will need to order the loin well in advance, especially with rind on."
Serve this feast with flour potatoes and lots of butter for an unforgettable Irish feast.
Traditional Irish Bacon, Cabbage and Parsley Sauce
Is there anything more quintessentially Irish than bacon and cabbage?

Servings
10Preparation Time
10 minsCooking Time
2 hours 0 minsTotal Time
2 hours 10 minsCourse
MainCuisine
IrishIngredients
About 2.25kg (5lb) loin, collar or streaky bacon, either smoked or unsmoked with the rind on and a nice covering of fat
1 Savoy or 2 spring cabbages
50g (2oz) butter
Freshly ground pepper
For the parsley sauce:
600ml (1 pint) full-cream milk
A few parsley stalks
Sprig of thyme
A few slices of carrot (optional)
A few slices of onion (optional)
Salt and freshly ground pepper
50g (2oz) roux (50g of melted butter mixed with 50g of plain flour)
About 50g (2oz) curly parsley, freshly chopped
Method
Cover the bacon in cold water in a large pot and bring slowly to the boil. If the bacon is very salty there will be a white froth on top of the water, in which case it is preferable to discard the water and start again.
Cover with hot water and the lid of the pot and simmer until almost cooked, allowing 20 minutes for every 2.2kg (1lb).
Meanwhile, trim the outer leaves of the cabbage and cut it into quarters, removing the core. Discard the core and outer leaves. Slice the cabbage across the grain into thin shreds.
If necessary, wash it quickly in cold water. About 20 minutes before the end of cooking the bacon, add the shredded cabbage to the water in which the bacon is boiling.
Stir, cover and continue to boil gently until both the cabbage and bacon are cooked — about 1¾ hours.
Lift the bacon onto a plate and remove the rind if you like. When the bacon is fully cooked it will peel off easily.
Strain the cabbage and discard the water (or, if it’s not too salty, save it for soup).
Add a generous lump of butter to the cabbage. Season with lots of ground pepper; it’s unlikely to need more salt, but add some if necessary.
You can make the parsley sauce while the bacon is cooking. Put the cold milk into a saucepan and add the herbs and vegetables (if using). Bring the mixture to simmering point, season and simmer for 4–5 minutes. Strain the milk, bring it back to the boil and whisk in the roux until the sauce is a light coating consistency. Season again with salt and freshly ground pepper. Add the chopped parsley and simmer on a very low heat for 4–5 minutes. Taste and correct the seasoning.