01 -
Wrap up the dough and pop it in the fridge for at least half an hour. To make the dough, dump in your egg yolk and splash in cold milk (a spoonful at a time) until things come together nicely. Before that, use your hands or a pastry tool to crumble the cold butter into the dry mix of cocoa powder, flour, powdered sugar, and salt, so it turns crumbly.
02 -
Let your shell cool down all the way before you start filling it. After you bake for 10 more minutes with the parchment and weights gone, remove those. Start by rolling out your cooled dough, pressing it into a 9-inch tart pan, snipping off the extras, and poking the bottom with a fork. Slap on some parchment and add pie weights (beans work, too). Bake at 350°F (175°C) for 15 minutes.
03 -
Wait about half an hour while the ganache chills in the tart shell, or until it's set. To make it, pour super warm cream (don’t let it boil) over the dark chocolate. Let it sit a couple of minutes, then stir until it’s creamy. Mix in salt and vanilla, then spread into your cooled shell.
04 -
Smear the thick pistachio cream all over your set chocolate layer. Toss into the fridge for around 30 or 45 minutes. When making the cream, put the pistachios and milk in a blender till smooth. Cook this in a saucepan with sugar, cream, and cornstarch over medium, swirling it till it thickens like pudding. Take it off the heat, splash in almond extract if you want, and let it cool a few minutes. Mix in about 1/3 cup more roasted pistachios before spreading the layer.
05 -
Carefully flood the pistachio layer with the glossy ganache, smoothing with a spatula. Just pour hot cream over chocolate and butter, then stir until silky before you do that.
06 -
Toss whole or chopped pistachios around the edge for a pretty finish. Chill it at least an hour, so you’ll actually get nice layers when slicing.