Cook the pasta in a large pot of salted boiling water according to package instructions until al dente. Reserve 1 cup of pasta water, then drain.
While the pasta cooks, blend the pistachios and garlic in a food processor until finely ground.
In a pan over medium heat, combine the ground pistachio mixture, heavy cream, and a pinch of salt and pepper. Cook for a few minutes until the sauce begins to thicken.
Reduce the heat to low and stir in the Parmesan cheese until melted and smooth. If the sauce is too thick, add some reserved pasta water until you reach the desired consistency.
Add the cooked pasta to the sauce, tossing to coat well. Cook together for 1-2 minutes to let the pasta absorb the sauce.
Serve the pasta garnished with crushed pistachios and additional Parmesan cheese on top.
Notes
Toast the pistachios lightly to enhance their flavor before blending.
Save some pasta water to help thin the sauce if needed and make it cling to the pasta.
Cook the pasta al dente as it will continue to cook slightly when tossed with the hot sauce.
Add the Parmesan cheese off the heat to avoid it becoming gritty.
Garnish with crushed pistachios and extra Parmesan cheese for added texture and flavor.