In a medium saucepan, heat the milk and salt to 85c, stirring frequently to stop the bottom scorching. When it is at temperature, remove from the heat, add 30g lemon/lime juice and stir to combine. Leave for 5 minutes. The milk should separate into curds and whey - the whey will be translucent. If it has not separated, add another tablespoon of citrus juice and leave for another 5 minutes. Repeat as necessary. When the mixture has properly separated, rest the mixture for a further 20 minutes.

Line a sieve with a clean cotton handkerchief or similar, pour in the curds and whey and leave to drain. Stir and press on the curds with a spatula to remove more liquid. The more you press the curds, the firmer the cheese will be - I like a firm curd! You can also twist the ends of the handkerchief to remove liquid if you are in a hurry.

Add the flour and salt to a food processor, stand mixer or bowl and mix to combine. Add the avocado and blend in. If not using a machine, just try to rub it in as best you can, as you would with pastry. Add the hot water a little at a time and blend or combine with your hands. I used 90g of water when I made this pastry, but you may need a little more or a little less, depending on your flour. Knead for about 5 minutes in a machine, or 10 minutes by hand. When ready, the dough should be moist and pliable, but not too sticky. Thoroughly scrape out the food processor, but do not clean. Wrap the dough in plastic and rest on the work surface while you prepare the vegetables.

Heat a large frying pan (I used a cast iron skillet) over medium heat and dry sauté the mushrooms until most of their moisture has evaporated and they are well browned - you may need to do this in batches. Turn the heat right down, stir in a sprinkle of salt, some black pepper and a clove of crushed garlic and deglaze with a glug of white wine or a splash of water/stock - scrape and stir to release all the tasty caramelised mushroom juice. Transfer to a container and set aside.

Turn the heat back up. In the same frying pan, add the cavolo nero and a sprinkle of salt. Stir occasionally until wilted - it won't release as much moisture as something like spinach, but should reduce in size. Transfer to the food processor, if using. Add the ricotta, half the pecorino Romano, 1 clove crushed garlic, lots of black pepper and the herbs and blend to combine. If working by hand, just mix thoroughly.

In the frying pan, over medium-low heat, sauté the red onion with a little drizzle of olive oil until softened and translucent, 10-15 minutes - you need only stir occasionally. Season and turn off the heat. Add to the cavolo nero-ricotta mixture.

Cut the dough into eight even pieces. Using a pasta machine, one at a time, run a piece of dough through the machine, starting on setting 1 and working your way up, until the dough is as thin as you can make it. I got up to setting 8 on my machine. You will need to add a little sprinkle of flour to the dough sheets occasionally to stop them sticking. Sticking is very, very frustrating, so definitely avoid that!

Preheat the oven to 200c. Lightly grease a cast iron skillet (or similar) with olive oil. When one sheet is complete, lay it in the pan, trimming as necessary. You want to create one even layer with a little overhang round the edges, as pictured. Drizzle in a touch of olive oil - no need to go nuts - and brush or rub over the pastry so it is mostly covered. Repeat with three more layers - one piece of dough makes roughly one layer.

Add the fillings. I started with the cavolo nero-ricotta mixture, then added the olives, then the onion and finally the mushrooms, but you do as you see fit. Sprinkle over the rest of the pecorino.

Trim the overhang so it is an even length and fold it over the fillings. Start rolling out pastry again. Add three more layers, but try to mostly cover the exposed filling, as the edges already have a lot of pastry from the overhang. For the fourth and final layer, cover the entire top, overhang and all, and trim or tuck at the sides so you have a nicely uniform pie top.

Beat together the yoghurt and egg and brush a thick layer over the pastry. Bake for about 15 minutes. Remove from the oven, brush with a further layer of yoghurt-egg wash and sprinkle sesame seeds over the top. Turn the pie so it cooks evenly and return to the oven to bake for a further 15 minutes or so. The pie is done when it is puffed and evenly browned all over.

Serve hot, warm or cold - it's delicious any which way!