Cook the pasta according to package directions until al dente. Drain and rinse under cold water to stop cooking. Set aside.
In a small bowl, whisk together peanut butter, soy sauce, rice vinegar, sesame oil, sriracha, brown sugar, and minced garlic until smooth.
Gradually whisk in hot water until the sauce is smooth and pourable. Adjust consistency with more water if needed.
In a large bowl, combine the cooked pasta and peanut sauce. Toss until the noodles are evenly coated.
Divide among bowls and top with sliced green onions, chopped peanuts, and any optional toppings like shredded carrots or cilantro. Serve warm or at room temperature.
Tips
For a protein boost, add cooked chicken, shrimp, or tofu.
Store leftovers in an airtight container in the refrigerator for up to 3 days. Add a splash of water before reheating to loosen the sauce.
If the sauce thickens too much, thin with a little warm water or extra soy sauce.