Step 1

In a large bowl, combine masa harina, salt, and water, kneading with your hands until a smooth ball forms. Masa should be moist but not sticky. Cover with plastic wrap and let rest about 30 minutes for the moisture to even out.

Step 2

While dough rests, prepare filling: Set a large frying pan over medium-high heat. Squeeze chorizo from casings into pan, discard casings, and cook chorizo, breaking up pieces, until it starts to get crisp, 3-4 minutes. Transfer chorizo to a plate and discard fat from pan.

Step 3

Reduce heat under frying pan to medium and add 1/2 Tbsp. vegetable oil. Add onion and cook, stirring frequently, until onion is tender, about 3 minutes. Add mushrooms and continue cooking, stirring often, until tender, about 10 minutes. Fold in cooked chorizo, then set mixture aside until cool enough to handle, about 10 minutes.

Step 4

Make an indentation in the masa with a spoon. Add 1/2 Tbsp. oil, the baking powder, and flour. Knead with hands until oil, baking powder, and flour have mixed in completely.

Step 5

Divide masa into 8 balls (each a generous 2 Tbsp. or about 1 3/4 oz.). Set aside a pinch of masa to test the oil. Keep masa covered to avoid drying out.

Step 6

Line a tortilla press with 2 sheets of thick plastic (such as a zip-top bag cut into pieces). Place a masa ball in between the plastic sheets and press to 5 1/2 inches. Gently remove the top plastic sheet. Place 2 Tbsp. filling and 1 Tbsp. mozzarella on one side of the pressed masa disc, leaving a 1/2-inch border on that side. Using the bottom plastic sheet, gently fold the masa disc over the filling, like a folded taco. Press edges with your fingers (through the plastic), sealing in the filling.

Step 7

Transfer empanada to a sheet pan lined with plastic wrap or waxed paper, and cover with plastic wrap or waxed paper to keep it drying out. Repeat to make remaining empanadas. Save any extra filling for another batch of empanadas or to serve over pasta.

Step 8

Heat remaining 1 cup oil in a large frying pan over medium heat. Test oil by dropping in the reserved piece of masa. If the masa bubbles, it’s ready. Gently fry 2 empanadas, turning once, until golden and edges are crispy, 2-3 minutes per side. Transfer to a paper towel-lined plate to absorb excess oil.

Step 9

Serve empanadas with a side of sour cream.