1. 1. Preheat the oven to 400°F (200°C).

2. 2. Toss the pumpkin cubes with olive oil, salt, and pepper, then roast for 25 minutes until tender.

3. 3. Cook the macaroni according to package instructions. Drain and set aside.

4. 4. In a saucepan, melt the butter over medium heat. Add the cooked macaroni, roasted pumpkin, vegetable broth, milk, garlic powder, and sage. Stir to combine.

5. 5. Mix in the cheddar and parmesan cheeses until melted and creamy. Season with salt and pepper to taste.

6. 6. For the brown butter crumbs, melt butter in a skillet over medium heat, add breadcrumbs, and cook until golden brown.

7. 7. Assemble the burger by placing a generous scoop of mac and cheese on the bottom half of each bun, topping with brown butter crumbs, and finishing with the top bun.

8. 8. Serve hot, garnished with fresh sage leaves.