1. To make the pesto, heat a small frypan on medium-low heat and add the walnuts. Toss for about 2 minutes, until the nuts are fragrant and toasted. Remove from the heat immediately.

2. Squeeze out any excess liquid from the defrosted spinach.

3. Add the walnuts, garlic, oil and 80ml (⅓ cup) water to a blender or food processor and blend until smooth. Next add the spinach and salt, and blend until smooth (if the mixture is too thick, add another splash of water). Pour the pesto into a bowl and stir through the lemon zest and half the lemon juice. Taste and if needed, season with more sea salt.

4. Bring a large pot of salted water to the boil, add the pasta and cook according to packet instructions, until al dente. Drain the pasta, retaining 1 cup of pasta cooking water. Add the spinach pesto to the drained pasta, along with a good drizzle of olive oil and enough pasta cooking water to loosen everything up. Season with sea salt and black pepper. To serve, sprinkle with red chilli flakes and squeeze over the remaining lemon juice.

Also try: Hetty McKinnon's pear streusel

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