Sweet Potato Black Bean Empanadas

Name: Sweet Potato Black Bean Empanadas
Ingredients: 2 ½ cups (300 grams) all-purpose flour; ½ teaspoon kosher salt; 8 ounces (226 grams / 2 sticks) cold unsalted butter, (diced); 2 large eggs, (beaten); 4 teaspoons olive oil, (divided); 1 (8 ounce / 225 gram) yam (sweet potato), peeled and chopped into ¼-inch pieces; Kosher salt and freshly ground black pepper; ¾ teaspoon ground cumin, (divided); ½ cup water, (divided); ¼ cup finely chopped onion ((½ small onion or 40 grams)); 1 clove garlic, (minced); ¾ cup (125 grams) drained and rinsed canned black beans; ¼ teaspoon ground coriander; ¼ teaspoon chili powder; Flour, (for rolling the dough); 1 egg, (beaten)