Chop the veggies for the stuffing. Peel the onion and the carrots. Wash the celery. Finely mince the onion, carrots and celery with a sharp knife or in a food processor.
Sauté the veggies. Heat a pan or skillet with olive oil. When hot, add in the vegetables and sauté for 5 minutes over high heat while stirring continuously.
Cook the rice. Reduce to medium heat. Add the rice and poultry seasoning to the pan with the veggies. Sauté for 2 minutes. Pour the vegetable broth on top, cover with a lid, and simmer for 20 minutes (or according to the cooking time of your rice).
Stir in the scooped-out butternut squash flesh, crushed walnuts, and cranberries. Give it a good mix. Adjust seasoning if necessary.
Fill the butternut squash boats with stuffing. They should be heaping full. Serve with chimichurri.