Preheat the oven to 200°C. Cut the butternut squash in half lengthwise and remove the seeds. Lightly score the flesh in a criss-cross pattern to release excess moisture during roasting. Drizzle with olive oil and season with salt and ground coriander.
Place the squash halves in the air fryer, cut side down, and cook at 200°C for approximately 40 minutes, or until tender. Alternatively, roast in a preheated oven at 200°C for 40–50 minutes.
Allow the squash to cool slightly, then scoop out the flesh. Weigh 325 g of roasted squash and blend until completely smooth. The amount of flour needed may vary depending on the moisture content of the squash.
Transfer the squash purée to a clean work surface and flatten into an even layer. Sprinkle with nutmeg and Parmesan, then sift the flour over the top. Make a small well in the centre and add the egg yolk.
Using a dough scraper, gently cut through the mixture and fold it over itself until the ingredients come together into a soft dough. Avoid kneading too much, as this can make the gnocchi tough. The dough should be tender and slightly tacky.
Divide the dough into four equal portions. Cover with a clean kitchen towel to prevent drying.
On a lightly floured surface, gently roll each portion into a rope approximately 2 cm thick. Cut into pieces about 2 cm long. Roll each piece into a small, smooth ball.
Arrange the gnocchi on a parchment-lined tray lightly dusted with flour. To create pumpkin shapes, use a toothpick to gently press evenly spaced vertical lines around each ball. Make a small indentation in the top and insert a piece of parsley stem. Alternatively, simply press a small indentation into each ball.
Place the tray in the freezer for at least 15 minutes to help the gnocchi hold their shape during cooking.
Bring a large pot of generously salted water to a boil. Carefully add the chilled gnocchi and stir gently to prevent sticking. Cook until they float to the surface.
Using a slotted spoon, transfer the cooked gnocchi to a plate in a single layer. Reserve approximately 240 ml of the cooking water for the sauce.
Meanwhile, heat the olive oil in a large frying pan over medium heat. Add the mushrooms, season with salt and pepper, and cook until softened and golden brown, stirring occasionally.
Add the finely chopped red onion and cook for approximately 2 minutes, until softened. Stir in the garlic and cook for another 2 minutes, until fragrant.
Add the chopped spinach and cook until wilted. Pour in the cooking cream, followed by 120 ml of the reserved gnocchi water, Parmesan and nutmeg.
Stir until combined, then simmer gently for a few minutes until the sauce thickens slightly. If needed, gradually add more reserved cooking water until you reach your desired consistency. Taste and adjust the seasoning.
Carefully add the cooked butternut squash gnocchi to the creamy mushroom and spinach sauce. Gently toss to coat without damaging their shape.
Serve immediately, garnished with freshly chopped parsley and extra grated Parmesan, if desired.