Butternut Squash and Cheddar Casserole - With greens

3 1/2 pounds butternut squash peeled and cut in 1/4-inch-thick slices (about 6 cups) 1 bunch spinach fresh, washed and stemmed, optional 2 tablespoons butter,[...]

1 large butternut squash about 2 pounds * 1 large onion chopped 3 cloves garlic minced, or to taste 1 tablespoons olive oil 1 teaspoon cumin ground 1 teaspoon[...]