Tasty Vegan Burgers

Name: Tasty Vegan Burgers
Cuisine: American
Ingredients: 1 1/4 pounds (565 g.) sweet potato or butternut squash; 1 tablespoon plus 2 teaspoons (25 ml.) extra-virgin olive oil; one cup (100 g.) walnuts, finely chopped; 2/3 cup (95 g.) finely chopped onion; 3 tablespoons (45 ml.) minced garlic (6 or 7 large cloves); 2 (14-ounce/398 ml.) cans black beans, drained and rinsed; 2 to 3 tablespoons (14 to 21 g.) 9-spice mix, to taste; 1/4 to 1/2 teaspoon fine sea salt, or to taste; a quarter cup (8 g.) lightly packed fresh flat-leaf parsley, finely chopped; 1/3 cup (75 ml.) easy barbeque sauce or store-bought; 1 cup (70 g.) spelt bread crumbs or breadcrumbs of your choice; 2 tablespoons (17 g.) gluten-free oat flour; homemade vegan mayo, or store-bought; sliced avocado; sliced red onion; easy barbecue sauce, or store-bought; sliced tomato