Heat the butter in a non-stick frying pan. Swirl to coat the entire bottom.
Spread the squash cubes on the bottom of the pan. Sprinkle lightly with salt and pepper. Cook over high heat for about a minute until the sides that touch the bottom of the pan are lightly browned. Using kitchen tongs, flip each cube over and brown the other side.
Add the sliced onion and chopped chorizo. Stir. Cook over medium heat with occasional stirring until the squash cubes are cooked through. By this time, the pieces of chorizo will be nicely browned and the onion slices will be soft and caramelized.
Turn off the heat. Stir in the parsley.
Transfer the cooked squash and chorizo to a serving bowl or plate. Sprinkle with sliced scallions. Serve with bread or rice.