Sunday Roast Turkey Burger with Gravy & Sweet Potato Chips

Name: Sunday Roast Turkey Burger with Gravy & Sweet Potato Chips
Prep time: 20 min
Cook time: 35 min
Total time: 55 min
Cuisine: British
Ingredients: 1.1 lb ground turkey (500g, good quality); 1/2 medium red onion (finely diced, about 60g / 2oz); 2 tablespoons parsley (chopped finely); 1 tablespoon lemon zest; 1 tablespoon dried thyme; 1 tablespoon garlic granules; 1 teaspoon sage; 1 teaspoon celery salt; 1/2 teaspoon sea salt (plus more to taste); 1/4 teaspoon ground black pepper; 2 medium sweet potatoes (about 400g / 14oz total, peeled and cut into sticks); 1 tablespoon olive oil (or coconut oil); 1 teaspoon dried rosemary; 1/2 teaspoon sea salt; 2 bunches asparagus (woody ends removed); 1 tablespoon olive oil; 1 teaspoon garlic granules; 3/4 cup chicken stock (180ml); 1 teaspoon arrowroot powder