Preheat oven to 350°, prepare a baking dish by coating lightly with olive oil. (I used a 8.5x8.5" square baking dish)
Peel the butternut squash, and slice in half lengthwise. Scoop out seeds, and cut into 1/2" thick "half moon" slices. Arrange squash in the baking dish in an overlapping fashion
In a skillet over medium heat warm 2 tbsp butter and 2 tbsp olive oil. Add shallot and garlic and saute, stirring frequently, for 4 minutes or until shallot is translucent and garlic is fragrant. Being careful not to burn garlic. Remove from heat and set aside.
In a small bowl combine breadcrumbs, grated parmesan, and chopped fresh rosemary, spoon 3 tbsp of reserved shallot butter mixture into the breadcrumb mixture and stir until well combined. Set aside.
Pour the remaining shallot garlic butter over the butternut squash, lifting squash slices to coat all squash with mixture. Season squash with salt and pepper
Next take the reserved breadcrumb mixture and sprinkle over the butternut squash.
Bake uncovered for 55 minutes or until squash is tender and breadcrumbs are browned and crisp
Serve immediately with a sprinkle of additional fresh rosemary on top
Notes
If breadcrumbs don't brown, finish the dish in the broiler for 2-3 minutes to achieve a toasty breadcrumb top.
In a pinch substitute finely chopped onion for the shallot