Preheat your oven to 400°F (200°C). Peel, seed, and cube the butternut squash into 1-inch pieces.
Toss the squash cubes with 1 tsp of olive oil, and season lightly with salt and pepper. Spread them evenly on a baking sheet.
Roast the squash in the preheated oven for 25-30 minutes until tender and lightly caramelized, stirring halfway through.
While the squash roasts, finely chop the onion and mince the garlic.
In a large pot, heat a small drizzle of olive oil over medium heat. Sauté the chopped onion and garlic until translucent and fragrant, about 3-4 minutes.
Add the roasted squash and 2 cups of vegetable broth to the pot. Bring to a simmer and let it cook for another 5 minutes to meld the flavors.
Transfer the mixture to a blender (or use an immersion blender directly in the pot) and blend until smooth. Return the blended soup to the pot.
Stir in 1 cup of white beans to boost protein and add creaminess. Heat gently for 3-4 minutes until warmed through.
Remove from heat and stir in the nonfat Greek yogurt for extra creaminess and tang. Adjust salt and pepper to taste.
For a crispy garnish, quickly fry the fresh sage leaves in a dry pan over medium-high heat for about 20-30 seconds until crisp.
Ladle the soup into bowls and top with the crispy sage leaves. Serve warm.