Sweet Potato Shepherds Pie

Name: Sweet Potato Shepherd's Pie
Ingredients: 1 tablespoon coconut oil; 1 kg grass fed beef mince; 1 large onion, chopped; 2 medium carrots, peeled and chopped; 2 celery stalks, chopped; 1 tin organic crushed tomatoes; 4 tablespoons tapioca flour; 4 tablespoons tomato paste; 2 tablespoons Worcestershire sauce (see above for my homemade recipe); 1 cup home made or natural beef stock; 1 tablespoon fresh thyme, chopped; Salt and pepper, to season