Bring a large pot of salted water to a boil.
Meanwhile, in a large skillet, heat the olive oil over medium-high heat. Add the onion and a pinch of salt, and cook for 2 minutes, stirring frequently, then lower the heat to medium and cook for 10 minutes, or until soft and starting to brown.
When the water is boiling, add the noodles to the pot and cook until al dente, about 5 minutes. Quickly drain, reserving 1 cup of the pasta water.
When the onion has softened, increase the heat to mediumhigh. Then, add the tomato paste, soy sauce and Crunchy Chili Onion. Stir constantly for 1 minute, until the mixture is combined and the tomato paste darkens.
Add ½ cup of the reserved pasta water and milk to the tomato mixture, stirring until smooth and fully combined, adding more pasta water if necessary. Bring to a light simmer, then remove from the heat and add the cooked noodles, tossing with the sauce until they are fully coated. Serve garnished with Parmesan cheese and basil.
