Boil your potatoes for 15-20 minutes or until tender.
Whilst potatoes are cooking, put your shredded cabbage in another large pan, pour boiling water over the cabbage and cook for about 5 minutes, until just tender.
Heat a tbsp of oil and fry eight rashers of bacon until crispy. Set aside. Then cut up the remaining two rashers into small pieces and fry for 3-4 minutes until slightly coloured.
Add the cabbage and spring onions to the frying pan with the bacon and heat through, stirring.
Drain the potatoes, add butter and season, then crush roughly with a masher. Stir the cabbage, bacon and spring onions (reserve some for decoration) into the crushed potatoes. Stir in the mustard. Cover with a lid and keep warm over a very low heat. This is your colcannon.
To poach the eggs, crack the eggs into the gently simmering water with a splash of vinegar and poach for 3 mins. For instructions on how to poach a perfect egg, see the notes below.
Spoon the colcannon onto four plates or bowls. Arrange the crispy bacon on top (2-3 rashers per portion).
Take the eggs out from the water with a slotted spoon and place on top. Season with black pepper and some spring onion.