Cold Sesame Noodles

Name: Cold Sesame Noodles
Ingredients: 1 pound Chinese egg noodles, spaghetti, or linguine; ½ teaspoon toasted sesame oil; 6 tablespoons sesame paste (tahini) or peanut butter; ¾ cup water, plus more if needed; 1 tablespoon rice vinegar or white vinegar; 3 tablespoons soy sauce; 1 ½ teaspoons sugar; 2 garlic cloves, minced; 1 scallion (both white and green parts), thinly sliced; 1 ½ inches fresh ginger, peeled and chopped (1 tablespoon); Chinese chili oil (optional)