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