Start by making the confit as this needs to be prepared ahead of time – the day before you want to serve it, if possible.
Take one and a half of the lemons and slice them into thin rings about 1/8 inch (3 mm) thick, discarding the end pieces and pips.
Place these in the non-aluminium saucepan and cover with sufficient cold water to just cover them, bring to a simmer for 3 minutes, then drain through a sieve and discard the water.
Now pour 12 fl oz (340 ml) water into the same pan, add the sugar, stir over a gentle heat until all the grains have dissolved then add the lemon slices.
Once the liquid has returned to a very gentle simmer lay the circle of silicone paper on the surface of the liquid – this will help the lemon slices to cook evenly.
Now continue to cook them at the very gentlest simmer, without a lid, for 45 minutes – until the skins are tender. Check them at 30 minutes by inserting the tip of a knife just in case they are cooking a little faster.
When they are tender, remove them with a slotted spoon to a shallow dish. The liquid will be much reduced at this stage, but what we want is about 5 fl oz (150 ml); if you have much more than this, increase the heat a little and reduce further.
Then squeeze the juice from the remaining half lemon, pour it into the syrup and pour this over the lemon slices.
Cover and leave overnight if possible.
To make the cheesecake, first of all pre-heat the oven to gas mark 6, 400ºF (200ºC), then prepare the base by crushing the biscuits – the best way to do this is to lay them flat inside a polythene bag then roll them with a rolling pin to crush them coarsely.
Then tip them into a bowl along with the flaked almonds and stir the melted butter into them. After that, press this mixture evenly and firmly on to the base of the cake tin and then place in the oven to pre-bake for 20 minutes.
After that remove it from the oven and allow it to get completely cold.
Meanwhile, remove the zest from the lemons using a fine grater (it can be grated on to a board and chopped even more finely if required).
Then take the juice from the lemons and measure to 5 fl oz (150 ml).
Next put 3 tablespoons of the lemon juice into a small bowl, sprinkle the gelatine over, then place the bowl in a small saucepan with 1 inch (2.5 cm) simmering water and leave it for 10 minutes to dissolve, or until it is absolutely clear and transparent.
Now put the egg yolks, sugar and ricotta cheese into a food processor or liquidiser and blend it all on a high speed for about 1 minute. Then add the lemon zest, remaining lemon juice and the gelatine, which should be poured through a strainer.
Blend everything again now until it's all absolutely smooth.
Then take a large bowl and whisk the double cream until you get a floppy consistency, then pour this in to join the rest of the cheese mixture and blend again, this time for just a few seconds.
Next, pour the whole lot over the biscuit base, cover with foil and chill in the refrigerator for a minimum of 3 hours.
To serve the cheesecake, carefully remove it from the tin on to a serving plate, decorate with a circle of lemon confit slices and serve the rest separately.
Note: this recipe contains raw egg.