Place the squash halved vertically, cut side up on a baking sheet. Brush with 1 tbsp butter, season with salt and ground black pepper.
Roast until the edges turn brown and the squash has turned soft, about an hour.
Meanwhile, in a large soup pot or dutch oven, add 1 tbsp butter, add chopped onions and celery; saute until the veggies turn soft.
Season with ground black pepper and salt.
After an hour-long roasting, take the squash out of the oven, scoop the flesh out, add it to the soup pot.
Add the chicken broth and milk, cook for 5 minutes stirring occasionally.
Transfer the soup in batches to a blender jar and puree or use an immersion blender and puree soup in the pot itself after lowering the heat.
Serve in soup bowls and garnish with sweet and spicy walnuts.
Making Sweet and Spicy walnuts
Place a small pan over medium heat, add 1 tbsp butter, let the butter melt, add brown sugar, chili powder, and salt.
Add the walnuts and toss them until evenly coated, let cool.
Notes
You could double the ingredients if you have more guests or save the leftover in the refrigerator. For a fancy presentation: serve the soup in the baked butternut squash after removing most of the flesh from it, make sure not to peel the skin off while scooping the flesh. Leave some flesh at the bottom to hold the soup without leaking.
Recipe by Cooking with Thas - Smart Cooking, Smart Living at https://thasneen.com/cooking/butternut-squash-soup-topped-with-sweet-and-spicy-walnuts/