Prepare your bowls and beaters by thoroughly washing them in hot soapy water and allowing them to dry (you can also use a clean tea towel). Egg whites won’t whip when fat is present so we want to make sure everything is as clean as possible.
Chop your pistachios, ready to garnish. Prepare your coffee and liquor mixture and pour it into a wide mouthed bowl (for easy and speedy savoiardi dipping).
Separate the eggs into clean two bowls. Make sure there is no egg yolk in the egg whites or your whites will not whip. Decant each clean egg white straight into the bowl you intend to whip them in. This way any accidents with the next egg white won’t ruin your first egg white.
At the end, you’ll have all 3 egg whites in your stand mixer or in a clean medium mixing bowl. Whip with the whisk attachment or hand beaters until they start to get frothy, then gradually pour in the caster sugar. Whip until stiff peaks form, then set aside.
If you are using only a stand mixer, carefully transfer the whipped egg whites into a large mixing bowl. If you are only using a hand beater, lightly clean off the beaters. If you are using both, lucky you (no additional work required).
Whip the egg yolks with the caster sugar for 3-4 minutes until lightened in colour and fluffy. Add the flavours, mascarpone and pistachio paste and combine on a low speed until everything has incorporated.
Very gently transfer the pistachio egg yolk mixture into the bowl of whipped egg whites. Use a spatula to carefully fold the pistachio mix into the egg whites. You want to keep in as much air as possible while still combining everything to form a smooth, light green and aerated pistachio mixture.
Gently spread a thin layer of pistachio mixture into the base of your serving dish. Dip your first savoiardi into the coffee mixture, flip it over and then immediately place it onto the pistachio base. Savoiardi break easily and quickly, so only give them a light dunk and work with a bit of speed.
Arrange your dipped savoiardi in the dish according to your preferences. Because 1 batch of my gluten free savoiardi makes more than this recipe needs, you can pack the savoiardi in snugly or you can leave a little room between each (and save the remaining savoiardi for eating with coffee). Personally, I like to pare back the savoiardi in this recipe and let the pistachio cream take centre stage. Do whatever you prefer!
Once you have a full layer of savoiardi, gently cover them with ½ the remaining pistachio cream. They are prone to catching in the pistachio mixture, so make sure you spread it carefully.
Repeat the process with a layer of dipped savoiardi, then top them carefully with the remaining pistachio cream. Sprinkle the chopped pistachios over the top and then place the tiramisu in the fridge for 4 hours+, ideally overnight.
Serve your Tiramisu straight from the fridge so the mascarpone doesn't lose consistency. Other recipes for pistachio Tiramisu specify that leftovers can be frozen - I haven't been able to test the theory as it immediately disappears from the fridge.