1. Take out a large saucepan with a tight-fitting lid and fill it with 2.5 liters of water from a kettle that has just boiled. Close the lid and bring the water back to a boil over a high heat on your hob. Place a large colander in the sink, enthusiastically open your bag of spinach leaves, and pour the contents into the waiting colander.
2. Get out a clean kitchen towel (not a terry cloth or waffle, just a smooth, thin one) and bring it to the stove. Once the water boils vigorously, add 1 tablespoon of fine salt, which will bring up the sparkling water. Wait for it to calm down, then stir well, and once the water is boiling again, add the pasta and stir with a pasta fork to help it submerge. Once the water returns to a boil, cook 2 min, stirring often to loosen and untangle the spaghetti. When the 2 minutes are up, remove the pan from the heat – but just to a nearby burner – cover with your kitchen towel and tighten the lid for 8 minutes, during which time you can prep your remaining ingredients.
3. Remove the lid and tea towel, toss the spaghetti well, then scoop out 500ml of the cooking liquid from the starchy pasta with a carafe or mug: this is what makes the sauce so luxuriously creamy. If you taste a sprig of pasta, you should find that it’s almost done, but still has a tiny bit of bite.
4. Drain the pasta in the colander filled with spinach – thus withering the leaves – and return the pot to the hob, leaving the colander in the sink for now. Quickly pour the peanut butter into the hot pan and add about ½ cup of the reserved pasta cooking water and mix well. It will look grainy and alarming at first, and when you look at the clotted clumps, you’ll think something’s wrong. This is not the case ! Just keep stirring, add the minced garlic, dried thyme, chili flakes, 2 tsp lemon juice, and 1⁄4 tsp salt, and you’ll quickly see a pale, herb-speckled emulsion . Slowly whisk in an additional 125ml pasta water until this is also smoothly incorporated.
5. Add the spag’n’spinachs and stir and toss in the pan (I use a few forks) to mix everything together as evenly as possible. You will need to keep adding more of the reserved pasta water because the pasta will continue to drink it up, so keep adding a little at a time, stirring vigorously but carefully; you shouldn’t have more than 50ml left, although you can use it all up. Taste the seasoning – you may need more salt or lemon juice – then serve, making sure to give everyone an equal amount of spinach. If desired, lightly sprinkle the top of each bowl with paprika. And, if you have half a lemon left, you can cut it into thin slices and give one to each person to squeeze while they eat.