Make the creamy sesame miso mixture. In a small prep bowl or a measuring cup, combine miso, tahini, peanut butter, sugar, rice vinegar, and water. Use a small whisk to stir until well blended. Set aside.

In a medium to large sauce pan, start boiling water for cooking somen noodles.

Meanwhile, start making the rest. Heat up another medium saucepan over medium heat. Pour neutral oil and add garlic, ginger, the white part of scallions, and red chili pepper flakes. Cook for 1-2 minutes until fragrant and slightly browned but not burnt.

Add water. Turn up the heat on medium high to bring to a gentle boil then reduce the heat medium low.

Add the creamy sesame miso mixture. Use a whisk to stir and mix until well blended. Keep the heat at medium low to simmer gently. Adjust the seasonings with sea salt if necessary. Continue to simmer gently until noodles are cooked. Right before serving, turn up the heat to reheat it.

Start cooking somen noodles in the boiling water for about 2 minutes. Drain and rinse under running water to remove some starch. Shake off the excess water then set aside.

To serve, pour the hot soup in a serving bowl and add the drained somen noodles. Top it with the green part of scallions, toasted sesame seeds, and a drizzle of toasted sesame oil for the finishing touch. Use optional toppings such as Japanese chili oil and extra rice vinegar as you like.