In a large pot, heat oil over medium heat. Add onion, celery, carrot and garlic and cook for 5 to 7 minutes, stirring occasionally, until soft and cooked through. Stir in flour and cook for 1 to 2 minutes.
Pour in the chicken stock and Natrel Lactose Free, making sure to stir up any brown bits at the bottom of the pan. Stir in miso until dissolved. Add potato cubes. Reduce, then cover and simmer for about 10 minutes, stirring occasionally. The soup should thicken slightly.
Add shrimp and scallops and bring to a boil. Reduce heat and simmer for 2-3 minutes. Taste and season with salt and pepper.
Enjoy immediately with freshly sliced green onions.