Preheat oven to 350°F.
To make dough, mix the flour and salt in a food processor or by hand. Add the butter, egg and water until a lumpy dough forms. Form a ball, flatten slightly and chill in the refrigerator for about 30 minutes.
For the filling, in a large pan add olive oil and onions and brown for about 5–7 minutes over medium heat. Add sweet potatoes, and cook until sweet potatoes are tender. Roughly chop the kale and add to the pan. Add garlic to the pan and cook together for 3 minutes. Set aside and add the ricotta cheese if using. Mix well and add coriander, cumin, apple cider vinegar, salt and pepper to taste.
While the sweet potato and kale mixture is cooling, roll out the dough into thin sheets. Use a plate or bowl to cut the dough into circles (a diameter of 4 to 6 inches works well).
Spoon filling onto 1 half of each round, to leave a 1/4-inch edge empty. Fold over dough into a half-moon shape. Use a fork to seal the edges and place onto an oiled baking sheet. Bake for 30 minutes.
While the empanadas are baking, make the Chimichurri. Place all ingredients in blender and mix until creamy. Add salt and pepper to taste. Serve with the empanadas.
TIP: If short on time, you can use nearly any kind of dough for empanadas: pizza dough, biscuit dough, piecrust dough or store-bought empanada rounds.