Preheat the oven to 120°C (250°F).

Toast the pistachios in the oven on a baking tray (sheet) for 45 minutes. Keeping the temperature low for a long period of time will allow the nuts to stay nice and green while removing all of the moisture. Once you’ve removed the pistachios from the oven, increase the heat to 125°C (255°F) to preheat for baking the tart. When the pistachios have cooled, add them to a food processor and blend until smooth, around 5 minutes.

Remove the stones from the dates and place the flesh into a food processor. If you feel as though the dates you’re using are a little on the bland side, add a little bit of icing sugar to boost the sweetness. If you’ve soaked dried dates, make sure they are well drained. They might blend better when they are a little wetter, but the taste will be that much nicer the more intense it is. Once the date puree is smooth, spread 150 g (5½ oz) over the base of the pastry shell. Set this aside while you prepare the custard mix.

Place the cream, salt, and sugar in a saucepan and bring to a simmer, then remove immediately. Next, temper the egg yolks in a mixing bowl by pouring a small amount of the hot cream mixture onto them and whisking the two together until incorporated. Add a small amount of the cream mixture to the pistachio paste and whisk to combine. Add the remaining mixture and the tempered eggs, then using a hand-held blender, blend until the mixture is shiny and smooth— to prevent any air from being incorporated into the mix, keep the head of the blender underneath the surface. At this point, you can add the smallest amount of yellow and green food colour to get a more vibrant pistachio hue as the egg yolk tends to brown the mix somewhat.

Pass the custard through a fine sieve into a measuring jug to use straight away—you want to keep it as warm as possible to ensure the mixture cooks evenly in the oven.

Place the pastry shell into the oven, then pour the custard over the date layer. Bake for 30 minutes, or until the custard is slightly wobbly in the centre, then remove from the oven and allow to cool.

Once the custard has completely cooled, remove the tart from the tin and portion into slices using a hot, sharp knife. To finish, dust each slice with a light coating of pistachio powder.