To make the dough, combine water and lard in a small saucepan and place over medium heat. Bring to a gentle boil and cook until lard has melted.

Meanwhile, combine flour, cornmeal, salt, and chile powder in a medium bowl. Make a well in the middle and pour the lard mixture into the well.

With a wooden spoon, slowly bring some of the flour into the water continuing to mix until fully incorporated.

Turn the dough onto a lightly floured surface and knead until smooth, about 3 minutes. Cover the dough in plastic wrap and refrigerate for 2 hours.

To make the sauce, combine water, brown sugar, and tamarind in a small saucepan. Bring to a boil over medium heat and cook, stirring occasionally until sugar is dissolved and tamarind is soft, about 10 minutes.

Strain mixture through a fine-mesh sieve into a heatproof bowl, pressing on the solids to extract as much of the liquid as possible.

Return the liquid to the saucepan and add remaining ingredients. Return to a boil and cook for 5-10 minutes or until thickened slightly. Set aside until cool.

To make the filling, heat oil in a large frying pan over medium-high heat. Add onions, chiles, and garlic and cook until starting to soften. Add coriander, cumin, salt, and pepper, and cook a few minutes more to toast the spices.

Stir in potatoes, peas, and lime juice and mix, mashing the potatoes slightly. Remove from heat and set aside.

Remove dough from the refrigerator and place on a lightly-floured surface. Roll out to about 1/4-inch thickness and cut into circles using a 4-inch round biscuit cutter. Gather scraps, form into a ball and return to refrigerator.

Using your finger, wet the edge of the dough circle with water. Place a tablespoon of filling on one half of the circle and fold the other half over to close, creating a half-moon shape. Press the two edges together to seal and use a small spoon to create a decorative edge if desired.

Repeat with the remaining dough, re-rolling the scraps until all the dough is used (you may have some filling leftover).

Heat the oil and lard in a large, deep frying pan over medium heat to 350°F or until a piece of bread browns in 30 seconds. Carefully add empanadas, 3 or 4 at a time and fry until golden on one side, about 3 minutes. Turn and cook until golden on the other side, about another 2-3 minutes.

Remove to a paper towel-lined plate and serve immediately with the tamarind dipping sauce.