Cook pasta to al dente, or according to package instructions. I have also used penne pasta instead of shells. Both taste great! Ensure to save 1/2 cup of cooking water before draining.
In a large saucepan, heat the olive oil, garlic, and green onion. Cook until soft.
Add tomato paste and cook for 2-3, until it appears darker in colour.
Add in the vodka and cook until evaporated.
Add in the heavy cream and red pepper flakes. Stir until combined. Add salt and pepper to taste. Remove sauce from the heat once thickened.
Once the pasta is cooked and drained, it's time to finish the sauce. Bring pan back to heat on medium. Add in the butter. Stir until melted.
Add in the pasta and past water. Stir.
Add Parmesan cheese and stir until combined. Add salt and pepper to taste.
Plate, top with Parmesan cheese and basil, and serve!