01 - Cook the udon noodles according to package instructions. Drain and set aside.
02 - In a large skillet over medium heat, heat the neutral oil. Add the onion and cook for 2 minutes until softened.
03 - Add the sliced shiitake mushrooms and sauté for 3–4 minutes until tender.
04 - Stir in the garlic and ginger, cooking for 1 minute until fragrant.
05 - In a bowl, whisk together the miso paste, soy sauce, sesame oil, heavy cream, and water until smooth.
06 - Pour the sauce mixture into the skillet with the vegetables. Bring to a gentle simmer and cook for 2–3 minutes, stirring frequently.
07 - Add the cooked udon noodles and baby spinach, tossing everything together until the noodles are well coated and the spinach is wilted.
08 - Taste and adjust seasoning if needed. Serve immediately, garnished with green onions, sesame seeds, and chili flakes if desired.