Heat the vegetable oil in a large pot over medium heat. Add the chopped onion and sauté for about 3 minutes until translucent.

Stir in the sliced tomato and shiitake mushrooms, cooking for another 2 minutes until the tomatoes soften.

Add the minced garlic and sauté for another minute until fragrant.

Pour in the water or vegetable broth and bring to a boil, then reduce to a simmer.

Stir in the miso paste and peanut butter until fully dissolved. Let simmer uncovered for 5 minutes.

Introduce the dry ramen noodles into the simmering broth and cook for 2-3 minutes, stirring occasionally.

Ladle the ramen into bowls, topping each with sweet corn, bean sprouts, and scallions. Add a soft-boiled egg if desired.

Finish with a sprinkle of white sesame seeds and serve hot.