Preheat oven to 400 degrees. Cut the butternut squash in half, seed and prick the inside a few times with a fork. Lay on a sheetpan, cut side up. Brush with a little olive oil, sprinkle with seasoned or garlic salt and pepper. Bake until tender, about 45 minutes. When cool enough to handle, scoop out the flesh and reserve. Discard peel.
In a sauce pan, heat olive oil and butter. Add the onions and carrots and saute for 2 minutes. Add the garlic and sage and stir for a minute. Sprinkle with flour and stir with wooden spoon for 1-2 mintues. Splash with white wine, stir to incorporate. Add the chicken stock and squash. Simmer for 20 minutes.
In the meantime, cut up sausage into 1/4 inch dice or half slices. Heat a small frying pan and add butter and oil. When butter is starting to turn brown, add the sage and fry until crispy. Remove sage leaves for garnish and then saute the sausage. Reserve. Blend the soup in a blender. Blend and add to clean saucepan. Add the cream, sherry, and sausage. Adjust seasoning. Garnish with fried sage leaves, croutons or crusty bread.