Slice carrot and pumpkin into bite-sized pieces. Chop cabbage into thirds and slice green onion thinly. Trim and separate shimeji mushrooms. Microwave pumpkin for 2 minutes at 600W.

Rinse oysters with salt and water multiple times, then drain.

Boil water in a pot, add dashi powder, carrot, shimeji mushrooms, and cabbage. Cover and simmer on low heat for 7–8 minutes.

Add frozen udon noodles, cover, and cook for 2 minutes. Stir to loosen noodles, then add salt, oysters, and green onion. Cook for 1–2 minutes until oysters are done.

Add pumpkin, milk, and dissolve miso into the soup. Mix well.