Harvest Stew

Name: Harvest Stew
Ingredients: 1 tablespoon olive oil; 1 large onion (peeled & chopped); 1/2 head of garlic (peeled & minced); 1-1/2 pounds ground bison; 2 pounds butternut squash (peeled & cubed); 30 ounces canned tomato sauce (I like Muir Glen); 2 cups vegetable broth; 1/2 teaspoon sea salt; 10 ounces fresh baby spinach