In a large, microwave-safe bowl, whisk together the vegetable stock, soy sauce, sesame oil, garlic powder, red pepper flakes, and sweet chili sauce. Microwave for 2 minutes. Whisk in the peanut butter and the whites of the scallions. Whisk until smooth.
Add the ramen to the bowl and turn it over several times to thoroughly coat it in the broth. Microwave for 1 minute. Flip the ramen and microwave for another minute. Stir until the noodles have separated and are coated in the flavorful broth. If the noodles are still a little firm, microwave for an additional 30 seconds.
Allow the noodles to sit in the broth for a few minutes. The broth will thicken into a sauce.
Serve warm garnished with the greens of the scallions and sesame seeds.
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Notes
To store: Transfer leftover peanut butter ramen to an airtight container and refrigerate for 2-3 days. Reheat in the microwave or on the stovetop over medium-low heat. When reheating, you may need to add a little water or broth to loosen the sauce as it tends to thicken when chilled.