Preheat oven to 400 and prepare baking sheet with parchment paper.
Chop butternut squash into 1-2 cm sticks.
Combine cornstarch and water in a small bowl, wait a few minutes to thicken.
Prepare 2 plates; one with all purpose flour, the other with panko mixed with a pinch of salt.
Coat squash pieces first in flour, dip into cornstarch mixture, then coat with panko crumbs (roll the squash pieces into the panko crumbs, pressing down to make sure it sticks). To avoid getting your hands sticky, use a fork to dip the squash in the cornstarch mixture.
Bake for 30min at 400 until browned and crispy.