Preheat the oven to 220C/430F/Gas 7.
To make the tea-smoked mackerel, you need a heavy roasting tin, a wire rack large enough to sit over the rim of the tin and an old wooden spoon. You will also need a sheet of foil folded double that is large enough to cover the rack and tuck in under the rim of the tin.
For the tea-smoked mackerel, dip a piece of kitchen paper in olive oil and lightly oil the rack and one side of the foil. Season the mackerel fillets with salt and freshly ground black pepper and place skin-side down on the rack. Drape the foil oiled-side down over the fish, leaving the overhang loose.
Make the smoking mixture by mixing the chamomile tea leaves, sugar and rice together in a bowl. Heat the roasting tin on the hob, moving it around to get an even heat. Scatter the smoking mixture over the bottom of the tin and stir it around with the wooden spoon. The sugar will melt and stick the tea to the rice, and then start to burn. Immediately set the rack with the fish over the tin and remove from the heat. Protecting your hands with oven gloves or a tea towel, tuck the overhanging foil tightly all around the rim of the tin. When the foil is sealed really tight and no smoke is escaping from the sides, turn the heat back on and continue to move the tin around for 30 seconds. Transfer to the oven to cook for five minutes.
Remove the tin from the oven and leave the fish to cool without unwrapping. Turn the oven down to 190C/380F/Gas 5. Line a large, heavy baking tray with baking parchment.
For the tarts, roll out the puff pastry on a lightly floured surface to a large, neat rectangle about 3mm thick. Place the pastry on the parchment-lined tray. Cover with another sheet of baking parchment, then set a second heavy baking tray on top to act as a weight. Bake for 8-10 minutes or until the pastry starts to turn a very light brown. Remove from the oven and take off the top tray and paper. Cut out eight discs from the pastry using a 7cm/2¾in plain cutter. Return the discs to the oven on the parchment-lined tray and bake uncovered for 3-4 minutes or until golden and crisp. Leave to cool on a rack.
Take eight metal chefs' rings, about 8cm/3¼in in diameter and 1cm/½in deep, and tightly cover one end of each ring with cling film like a drum skin. Set the rings on their covered ends on a tray, and place into the fridge to chill.
Break the duck eggs into two separate cups. Bring 1 litre/1¾ pints of water and the vinegar to a gentle simmer in a large saucepan. Stir the water clockwise, then carefully drop the eggs into the vortex and poach for six minutes. Lift the eggs out with a slotted spoon and place them in a bowl of iced water. Leave to cool. When the eggs are cold, remove them from the water and drain on kitchen paper. Chop the eggs coarsely and place them in a bowl. Cover and transfer the eggs to the fridge.
When the mackerel is cool, remove it from the rack and peel away the skin. Check for any small bones with your fingers, then flake the fish into a bowl. Add the chives, lemon juice and one-third of the mayonnaise, then add the crab and lightly fold everything together. Take care not to break up the fish - you want large chunks. Stir in half of the chopped eggs and add salt and freshly ground black pepper to taste.
Divide the mixture into eight equal portions and press into the chilled metal rings. Mix the rest of the chopped eggs with just enough of the remaining mayonnaise to bind. Taste and add more salt and freshly ground black pepper if necessary.
To serve, dab a little mayonnaise in the middle of each plate. Place a pastry disc in the top of each metal ring and carefully turn the ring over onto the plate, so the pastry is on the bottom and held in place by the mayonnaise. Remove the cling film. Push the fish mixture down in the ring with a small spoon so that it presses onto the pastry and lift off the ring. Garnish the tops of the tarts with spoonfuls of the egg mayonnaise.
Type the ingredients you want to use, then click Go. For better results you can use quotation marks around phrases (e.g. "chicken breast"). Alternatively you can search by chef, programme, cuisine, diet, or dish (e.g. Lasagne).