Place cubed chicken in bowl. Add 4 tbsp of prepared chimichurri sauce and marinade as grill comes to temperature. Alternatively, you can marinate for up to 24 hours in the fridge,
Heat a large, heavy skillet on high heat.
Heat a pan over medium heat. Add the chicken cubes until cooked through to an internal temperature of 165 degrees, about 6 minutes.
Add water to a large stock pot and bring to boil.
Generously salt water and add in pasta.
Cook pasta to just under al dente (should be flexible but with a bit of crunch still.)
Remove 1 cup of pasta water and add to pan with chicken, bring to a boil.
Drain pasta and add to pan with chicken and boiling pasta water.
Stir in 1/2 cup chimichurri sauce and toss as pasta water cooks down.
Taste and add up to 1/2 cup more chimichurri sauce, depending on your taste.
Garnish with parmesan cheese and serve.