In the meantime, blitz your pistachios in a blender until you get a powdery consistency. You can also opt for a coarser consistency if you prefer a lot of crunch.
Add the ground pistachios to the pan with the onions and bacon, along with 8 tablespoons of pasta cooking water. Mix well and leave to cook at low heat for 2 more minutes.
Drain the pasta and save some more cooking water, about half a glass.
Transfer the pasta to the same pot and add the onions, bacon and pistachios paste. Mix well.
Then add the cream cheese, about 3 large tablespoons, and fold it in with the pasta and the rest of the ingredients. Add more pasta water as needed. Continue mixing for 2 to 3 minutes so that the cream cheese heats up and melts fully.
Take the pot off the heat, and serve the cream cheese pasta in your plates.
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Notes
Make sure to serve the pasta quickly and enjoy it right after. This kind of pasta tends to get sticky and dry pretty quickly.