Boil the pasta in salted water according to package instructions. Reserve ¼ cup pasta water, then drain and set aside.
In a blender or food processor, combine deseeded jalapeños, cilantro, and tomatillo salsa verde. Blend until smooth.
In a saucepan over medium heat, add the heavy cream and warm it gently until it is hot but not boiling. Then add the softened cream cheese cubes, whisking continuously until fully melted and smooth. If needed, reduce the heat to medium-low to prevent scorching.
Stir in the ranch seasoning and jalapeño cilantro purée. Bring to a simmer over medium heat, then reduce to low heat, stirring frequently until the sauce is heated through and slightly thickened, about 2 to 3 minutes.
Remove the sauce from the heat and stir in the sour cream until smooth and creamy.
Add the cooked pasta to the sauce and toss to coat. Thin with reserved pasta water if desired, a little at a time, until you reach your preferred consistency.
Serve warm. Top with additional cilantro.
Notes
*Depending on your heat preference and the size of the jalapeños available. I recommend 3 small/medium or 2 large jalapeños. If you're sensitive to spice, start with less.Storage: Store any leftovers in an airtight container in the refrigerator for 3 to 4 days. Reheat gently in the microwave, adding a splash of milk if the sauce has thickened too much. This pasta is not ideal for freezing, as the cream-based sauce may separate when thawed and reheated.