Duck eggs are a little richer. If my local poultry store couldn't order them in then I'd just use some extra large chicken eggs and not think the dish inferior because of it.
Anyway. The version in the book is, as I said, different to the one I tasted.
Poached duck egg with salt and vinegar cabbage
- Cook 10 eggs in water bath at 64.5C/50 minutes. Immerse in ice water. Peel eggs. Discard the outer layer of white. Set peeled eggs aside on moist kitchen towel.
- Discard outer leaves of 1 head of Savoy cabbage. Pick the rest of them, discard stems and slice into chiffonnade. Blanch in lightly salted water then dunk in ice water. Strain.
- Reduce 500mL chicken stick by two thirds. Use immersion blender to stir in 200g butter (yeah, really). Season w/ salt, pepper and lemon juice. Store at room temperature.
- Make cavolo nero powder by removing stems of 200g cavolo nero, blanching leaves and parking in a dehydrator (no setting/temperature specified) for 4-6 hours until dry and crisp. Grind to fine powder in spice grinder.
- Remove stems from 300g kale, blanch leaves (same method as the first two sets of leaves), cut into 'smaller shapes', brush w/ extra virgin olive oil and season w/ salt. Dehydrate in same fashion as the cavolo nero but do not turn it into a powder.
- Use paring knife to remove individual leaves from 300g Brussels sprouts. Ensure leaves are dry then deep fry half of them in 150C canola oil until they start to colour. Drain, season and keep warm in food dehydrator.
- Blend 15g freeze-dried sherry vinegar until you have a fine powder. Blend with 15g Malto.
- Reheat eggs in combi oven at 55C for 15 minutes then season w./ salt and pepper. Use tea strainer to dust w/ cavolo nero powder. Reheat Savoy cabbage in the butter/stock mixture and season. Steam the Brussels sprouts leaves (not the deep-fried ones, the half you left untouched) w/ chicken stock then toss in butter and season.
- Plating: Savoy cabbage in the middle of the plate w/ an egg on top. Starting w/ steamed Brussels sprouts, build a pile of steamed and deep-fried leaves in a neat pile resting against base of egg. Finish with kale on top of that pile. Dust dish with a little of the vinegar powder.
Good luck finding freeze-dried sherry vin.