Grease a 7x11-inch casserole dish and preheat the oven to 350 degrees F.
In a large bowl, combine butternut squash, brown sugar, eggs, milk, butter, flour, vanilla, and salt. Use a hand-held mixer to beat until smooth.Transfer to prepared baking dish.
In a medium bowl, stir together all topping ingredients until mixed evenly. Sprinkle on top of butternut squash mixture.
Bake for 30 minutes.
Notes
To cook butternut squash, cut in half lengthwise. Place cut side down on a baking sheet lined with foil or parchment paper. Bake at 350 degrees for 45 to 55 minutes, or until soft.