• Heat the olive oil in a medium saucepan over medium heat. Add the onion, and cook, stirring occasionally, until soft and just golden brown, 5-8 minutes. Add the garlic, jalapeños, chili powder, and cumin and cook until fragrant, about 1 minute. Add the sweet potato, stock, and tomatoes with their juices and bring to a boil. Add 1/4 tsp salt, cover loosely, and reduce the heat to medium low. Simmer until the sweet potatoes are completely tender, 30-35 minutes. Uncover the pot, add the kale, and cook until just wilted, about 3 minutes.
• Meanwhile, line a plate with paper towels and set near the stove. In a small, shallow skillet, heat 1 in/2.5 cm olive oil over medium heat. To test the temperature of the oil, drop a tortilla strip into the skillet; the oil should sizzle and the tortilla cook to a pale golden brown. If it turns dark brown quickly or the oil is smoking, reduce the heat. Working in batches, fry the tortilla strips until golden brown, 1-2 minutes. Transfer the tortilla strips with a slotted spoon to the paper towel-lined plate and immediately season with salt.
• Ladle the soup into bowls and garnish with fried tortilla strips, yogurt, queso fresco, and cilantro, plus additional toppings such as avocado and radishes at your whim. Serve warm with the lime wedges.

For tortillas

• Pulse the shortening, flour, 1 tsp sel gris, and baking powder in a food processor for about 20 seconds. Add the warm water and pulse together until just combined, about 15 seconds. Transfer the dough to a lightly floured work surface and knead until soft and smooth.
• Cut the dough in half with a bench scraper or a knife, and cut each half into eight pieces, about 1 1/2 oz/40 g each. Form each piece into a small ball with your hands and cover with plastic warp. Flatten the balls, one by one, on a lightly floured work surface and roll with a rolling pin to about 8″/20 cm wide, turning constantly to keep their round shape.
• Preheat a large cast-iron griddle pan or a two burner griddle pan on the stove top over high heat. Place a plate and a kitchen towel near the griddle pan.
• Let one edge of the tortilla touch the griddle, then lower your hand slightly and move it away from you, allowing the tortilla to roll onto the griddle.
• Cook until lightly browned with a few bubbles, 3-4 minutes. Flip the tortilla with tongs, a spatula, or your fingers. It should be pale golden brown. Continue cooking on the other side until the tortilla puffs and separates and then deflates, 2 to 3 minutes more. Stack on a plate as you remove them from the griddle and cover loosely with a kitchen towel to keep warm. Serve warm, or cool completely, wrap tightly, and keep on the countertop for the next day.