Preheat your oven to 400°F (200°C).

Prepare the butternut squash: Peel the squash using a vegetable peeler (microwave it for 2-3 minutes to soften the skin). Cut the squash in half, scoop out the seeds, and then cut the squash into 1-inch cubes.

Toss the squash with olive oil, salt, and pepper: In a large bowl, toss the cubed squash with about 2 tablespoons of olive oil, salt, and pepper. Make sure the squash is evenly coated.

Roast the squash: Spread the squash in a single layer on a baking sheet. Roast for 25-30 minutes, or until the squash is tender and slightly caramelized, flipping halfway through.

Sauté the onion and garlic: While the squash is roasting, heat 1 tablespoon of olive oil in a large pot or Dutch oven over medium heat. Add the chopped onion and cook until softened, about 5-7 minutes. Add the minced garlic and cook for another minute, until fragrant.

Add the roasted squash, apple, and sage to the pot: Once the squash is roasted, add it to the pot with the sautéed onion and garlic. Add the chopped apple and fresh sage leaves.

Pour in the vegetable broth: Pour in 4 cups of vegetable broth. Bring the mixture to a boil, then reduce heat and simmer for 15-20 minutes, or until the apple is tender.

Blend the soup: Carefully transfer the soup to a blender (or use an immersion blender) and blend until smooth and creamy. If using a regular blender, be sure to vent it properly by removing the center piece of the lid and covering it with a towel to prevent splattering. If the soup is too thick, add more vegetable broth until you reach your desired consistency.

Season to taste: Taste the soup and season with salt and pepper as needed. You can also add a pinch of nutmeg or a drizzle of maple syrup for extra sweetness, if desired.

Serve and garnish: Ladle the soup into bowls and garnish with your favorite toppings such as toasted pumpkin seeds, a swirl of cream, a drizzle of olive oil, croutons, and chopped fresh parsley.