Brown the beef:
Heat the olive oil in a large (at least 4-quart) saucepan over medium-high. Add the ground beef, 1/2 teaspoon salt, and black pepper. Cook, breaking up the meat with a wooden spoon, until no longer pink, 5–6 minutes.
Add aromatics & build the sauce:
Stir in the garlic and cook until softened, about 2 minutes. Add the Thai Basil Marinara, Thai chili flakes, and fish sauce. Bring to a boil, then reduce to low and simmer, partially covered, until the sauce thickens slightly, 15–20 minutes.
Blanch the green beans:
Meanwhile, bring a large pot of generously salted water to a boil. Add the green beans and cook until bright green, about 1 minute. Use a spider or sieve to transfer them to a bowl of cold water; drain well.
Cook the pasta:
Cook the quattrotini in the same boiling water to al dente. Reserve 1 cup pasta water, then drain.
Bring it all together:
Add the cooked pasta and blanched green beans to the sauce. Stir to coat, adding splashes of the reserved pasta water to loosen as needed. Cook 3–4 minutes to warm through and let the flavors meld.
Serve:
Divide among bowls and garnish with fresh Thai basil.
