Stir sour cream, sorrel, lime juice, 1 teaspoon salt, and sugar in a bowl until well combined. Refrigerate until ready to use.

Mix flour, masa harina, baking powder, and 2 teaspoons salt in the bowl of a stand mixer. Gradually pour butter and water into flour mixture while mixing at lowest speed; mix until a dough just starts to come together.

Turn dough out onto a clean, flat surface and knead 3 to 4 times. Separate dough into 1 1/2 ounce balls, cover, and let rest for 1 hour.

Press each dough ball in a tortilla press lined with parchment paper or plastic wrap; transfer each tortilla to a baking sheet.

Lightly coat a cast-iron pan with 1/2 teaspoon vegetable oil and heat over medium-high heat. Place a tortilla in the pan and cook until lightly golden, about 1 minute per side. Repeat with remaining tortillas.

Heat 1/4 cup vegetable oil in a skillet over high heat. Stir in chicken; cook until browned around the edges, 4 to 6 minutes. Stir in onion, kale, 1 teaspoon salt, and pepper; reduce heat to medium-high. Cook, stirring often, until kale is wilted, 3 to 5 minutes. Remove from heat.

Spoon chicken-kale mixture into each tortilla, top with sorrel sour cream, and serve.