Cut the squash in half and discard the seeds. Remove the skin, cut the squash again length-wise, and cut the squash crosswise into ¼-inch slices.

Place the black beans in a small bowl. Cover with warm water, soak for 5 minutes, and then drain. Rinse 3 to 4 times to remove the excess salt and loose skins and drain well.

In a small bowl, mix together the cornstarch and 1 teaspoon water.

Heat a wok or nonstick skillet over high heat. Add the vegetable oil, black beans, garlic, and squash. Stir-fry over high heat for 2 minutes and add the broth. Cover and cook for 3 minutes. Add the soy sauce and stir well. Stir in the cornstarch mixture and cook until the sauce thickens, 1 to 2 minutes. Add the green onions, stir, and cook for 30 more seconds.