Black pudding bubble and squeak with eggs and hollandaise

Method

1. Cook the potatoes in boiling salted water until just tender but not falling apart (about 20 minutes). Drain and leave uncovered to go cold; if you can chill them, all the better.
2. Melt the butter in a small pan, add the onion, season lightly, then cover and cook over a low heat for 10 minutes or until soft and translucent but not browned. Leave to cool.
3. Remove and discard any large stalks from the greens and roughly tear the leaves. Drop them into boiling salted water and cook for 2-3 minutes until tender. Drain, refresh under running cold water, drain once more, then squeeze out the excess liquid. Roll up in a clean tea towel and leave to dry – the potatoes and greens need to be really dry to make the cakes crisp – then coarsely chop.
4. Cut the potatoes roughly into 2cm chunks. Skin the black pudding and cut into smaller pieces. Heat 1 tbsp of the olive oil in a large non-stick frying pan and fry the black pudding for 1-2 minutes until just crisp all over. Transfer to a large mixing bowl and leave to cool.
5. Add the potatoes, cabbage and onion to the black pudding and season generously. Stir to combine, then shape into 4 cakes by firmly pressing a quarter of the mixture at a time into a 9cm plain pastry cutter or cooking ring. This will prevent them falling apart when you cook them. Cover and chill for 1 hour.
6. Shortly before you’re ready to cook the cakes, bring a pan of water up to the boil, add a pinch of salt and the vinegar, then lower the heat so only a few bubbles are rising up from the base of the pan. Break one of the duck eggs into a teacup. Swirl the water with a wooden spoon to create a whirlpool, gently slide the egg into the centre of the pan, then leave it to poach for 3-4 minutes. Remove with a slotted spoon to a plate and repeat with the remaining eggs. Leave the water simmering over a low heat.
7. Return the frying pan to a medium-high heat. Add the rest of the oil and, when it’s hot, add the bubble and squeak cakes. Fry them for 6-7 minutes on each side until crisp and golden brown.
8. Meanwhile make the hollandaise. Melt the butter in one small pan and put the vinegar and lemon juice in another small pan. Put the egg yolks, sugar and a pinch of salt in a mini food processor (or whisk in a medium bowl with an electric hand mixer). Bring the vinegar and lemon juice up to the boil and, with the motor running/while whisking, gradually add it to the yolks. Bring the butter up to the boil, then add it in a slow trickle, whisking, until the sauce is smooth and thick.
9. Slide the poached eggs back into the hot water and leave for 30 seconds to heat through. Scoop them out onto kitchen paper and briefly drain. Lift the bubble and squeak cakes onto warmed plates and top each one with a poached egg. Spoon some of the hollandaise sauce over each egg and scatter with the chives.