Place Butternut Squash (2 pound) into a deep heatproof bowl and cover with plastic wrap and make holes on the plastic wrap. Microwave for 5 minutes using heat function on P8 (or at 800W) until soft.
Add Onion (1) and Garlic (2 clove) into a bowl, add Oil (2 tablespoon) and stir to combine. Cover with plastic wrap and microwave on high for 3 minutes using heat function on P10 (or at 1000W) until soft.
Combine onion mixture with squash and Vegetable Broth (2 cup). Season with Salt (to taste) and Ground Black Pepper (to taste). Blend using an immersion blender until smooth. Taste and adjust seasoning as needed.
Add the Bucatini Pasta (1 package) into a heatproof tray and cover completely with Water (2 cup). Add a generous pinch of Salt (1 tablespoon). Microwave for 2 minutes using heat function on P10 (or at 1000W).
Take out pasta and stir to prevent sticking. Then place the pasta back in the microwave, cook for 3 more minutes using heat function on P8 (or at 800W), until the pasta is slightly softened. It will finish cooking in the butternut squash sauce.
Combine the butternut squash sauce and the semi-cooked pasta together in a big heatproof bowl and cook in the microwave for 5 minutes using heat function on P8 (or at 800W).
Give the pasta a good mix after taking out. Put the pasta back to the microwave, cook for 4 more minutes on P8 (or at 800W), until the pasta is completely cooked.
Add the Sage Leaves (1 bunch) into a heatproof bowl, mix in the Oil (1 teaspoon), and microwave for 2 minutes on P10 (or at 1000W) until the leaves are crisp.
Garnish the butternut squash carbonara with sage leaves and grated Parmesan Cheese (to taste). Serve. Cooking results may vary depending on microwave oven use.