Method
Make the mayonnaise
1. If you’re using whole mackerel take the bones and heads and place in a deep pan. Roast on 180° for 20 minutes. Add 1 litre of oil and return to the oven for a further 20 minutes. Leave to cool overnight. Pass through a fine sieve and discard the bones. If you’re using prepared mackerel fillets then vegetable oil can be used instead.
2. Put the mustard, vinegar, salt, sugar and egg yolks in a food processor and blitz to combine. Very slowly pour in the oil to create the mayonnaise.
3. Set aside.
Prepare the crispy shallots;
1. Peel the 2 shallots and remove the root but leave whole. Thinly slice and dry on a j-cloth. A meat slicer is ideal to ensure regularity of the slices.
2. Heat oil in a large pan, or deep fat fryer to 170 degrees and fry the shallots until golden. Set aside to drain on kitchen paper.
Prepare the celeriac;
1. Wrap the whole celeriac in tin foil with 1tbsp of vegetable oil, a pinch of salt and 2 pinches of black pepper. Roast in the oven at 180° for 40 minutes. Allow to cool in the fridge completely.
2. Once completely cool, half the celeriac.
3. Slice one half of the celeriac into 1mm rounds (ideally on a meat slicer) and then cut into rectangles approx. 8mm x 11mm.
4. Set the celeriac aside.
Make the cannelloni;
1. Peel the remaining half of the celeriac and finely grate it into a large bowl.
2. Peel, core and grate the apple into the same bowl and mix.
3. Add 1tbsp of the mackerel (or plain) mayonnaise and a pinch of chopped chives and combine. Salt and pepper to taste. Add a little more mayonnaise to the salad if it is too dry to bind it.
4. Place 1tbsp of the celeriac and apple mixture at the end of each celeriac sheet and roll to form a cylinder – roll from the filling side to completely encase the filling.
Cook the mackerel
1. If using whole mackerel, fillet and de-bone the fish and place the fillets in the brine for 10 minutes. If using prepared fillets, skip this step.
2. Take 4 squares of oiled parchment paper and place in a hot pan. Add the mackerel fillets onto the paper one at a time, skin side down. The paper will ensure an even crisp skin is achieved. As the mackerel hits the heat press firmly with a fish slice to prevent it curling. It will relax after a few seconds to allow you to add the next fillet.
3. Cook for 2 minutes skin side then flip and cook the flesh side for 30 seconds.
To plate
1. Pipe 1tbsp of the mackerel (or plain) mayonnaise to the left of the plate and smooth across the plate using a small pallet knife.
2. Dress the rolled cannelloni with the vinaigrette and a few chives, place this on the mayonnaise.
3. Sprinkle the mackerel skin with crispy shallots and some thinly sliced apple and place in the centre of the plate.