In a small bowl, soak the cashews in hot water directly from the kettle, while you work through the next few steps.
Blanch the spinach in boiling water for a couple of minutes until soft, then strain it, reserving the leftover water. Transfer the spinach to a small blender, add 3 tablespoons of the reserved spinach water and blend until smooth. If you don’t have a small blender, you can use a handheld one to blend everything together in a bowl.
Next, add the flour to a large mixing bowl along with a generous pinch of salt. Make a well in the middle, pour in the blitzed spinach, then mix everything together. Transfer the dough to a floured surface and knead for 5 minutes, then wrap it tightly in baking paper and refrigerate for 30 minutes.
Divide the chilled pasta dough in half and roll each piece out until it’s as thin as you can get it without splitting the dough (this should be around 2 mm). Use a pastry cutter 8cm in diameter or the rim of a pint glass to cut the dough into circles. Repeat until all of the dough is used up and you’re left with 20 circles.
Drain the cashews and add them to a blender along with the juice from the lemon, basil and 3 tablespoons of cold water. Blend until the mixture reaches a smooth but thick consistency, then season well with salt and pepper.
Add a heaped tablespoon of the cashew mixture to the centre of a pasta circle and cover it with another circle. Use your thumb to press down around the edges, sealing the circles together. To finish, use the prongs of a fork to pinch all around the edges. Repeat until you’re left with 10 filled ravioli.
Bring a saucepan of water to the boil and cook the ravioli for 5 minutes, until tender, then carefully scoop out using a slotted spoon. We usually cook the ravioli in two batches to avoid them sticking together.
Meanwhile, finely slice half a dozen or so basil leaves and mix them in a small bowl with 2 tablespoons of extra virgin olive oil. Drizzle the basil flavoured oil over the ravioli to serve.