Preheat the oven to 375 degrees F. Line a rimmed baking sheet with foil. Rub the butternut squash halves with the oil and place cut side down on the baking sheet. Roast 35-45 minutes or until fork tender.

When cool enough to handle, scoop out the butternut squash flesh and purée in a food processor until smooth. You'll end up with roughly 4 – 4 1/2 cups of purée.

Transfer the purée to a fine mesh sieve lined with cheesecloth placed over a bowl. Cover loosely with plastic wrap and let stand in the refrigerator overnight to allow liquid to drain from the purée.

Preheat the oven 350 degrees F when you're ready to bake the casserole, and spray an 8×8" baking dish with cooking spray.

Beat the butternut squash, eggs, maple syrup, milk, butter, cinnamon, vanilla and salt until smooth, then pour into the prepared baking dish.

Combine the oats, flour, brown sugar, pecans, cinnamon and pinch of salt in medium bowl.

Cut in the cold butter in with a pastry blender, fork, or your fingers, until it's in pea-sized clumps.

Sprinkle the streusel evenly over the top of the butternut squash filling and bake at 350 degrees F for 45 minutes or until the streusel has browned and puffed up in the center.

Cool on a wire rack for about 10 minutes, then serve.