Fill a large pot with water and place over medium-high heat.
Once the water boils, add a small handful of salt and add the pasta. Allow the pasta to boil, stirring occasionally, until al dente (slightly firm to the bite). Remove pasta from heat and drain into a colander. Set pasta aside in a large mixing bowl until ready to use.
Place avocado, 1 cup stock, pepitas, garlic, lemon juice, and cumin into the well of a blender and puree until smooth, adding more liquid as needed. Season with salt and pepper.
Pour sauce over pasta and toss together until evenly coated. Transfer to serving plates/bowls and finish with more pepitas, red pepper flakes and fresh basil leaves. Serve immediately.