Set dough aside to rest for 10 minutes. 

In a small microwave-safe bowl, combine onion, juice from half the lime, 1 tsp water, ½ tsp sugar (2 tsp water and 1 tsp sugar for 4 servings), and a pinch of salt and pepper. Cover tightly with plastic wrap. Microwave until onion is softened and bright pink, 30 seconds. Carefully remove plastic wrap and stir. Set aside to pickle, stirring occasionally.

Place sour cream in a separate small bowl. Add water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt and pepper to taste.

Divide dough into 8 4 equal portions (16 8 portions for 4 servings); shape each into a ball. On a clean work surface, flatten each ball into a ¼-inch-thick round using the palm of your hand. TIP: If dough feels sticky, spray your work surface and hands with nonstick cooking spray.

Divide remaining mozzarella between tops of half the dough rounds. Top with remaining dough rounds and press edges of dough rounds together to seal to form arepas. TIP: Pinch and press edges while gently pressing down on tops of sealed arepas using the palm of your hand to ensure no cheese escapes while they cook! 

Heat a ⅓-inch layer of oil in a large, preferably nonstick, pan over medium-high heat. Once oil is hot, carefully add two arepas to pan. Cook until bottoms begin to brown, 2-3 minutes.  

Carefully flip arepas. Cook until opposite sides begins to brown, 2-3 minutes. Carefully transfer to a baking sheet. Repeat with remaining arepas. TIP: The oil will get hotter with each batch. If arepas begin to brown too quickly, reduce heat to medium.

Once all arepas are browned, bake on middle rack until dough is cooked through and cheese has melted, 10-12 minutes. Let pan cool slightly, then carefully wipe out.

While arepas bake, pat chicken* dry with paper towels and season all over with Mexican Spice Blend, salt, and pepper. 

Heat a large drizzle of oil in pan used for arepas over medium-high heat. Add chicken; cook until browned and cooked through, 3-5 minutes per side. TIP: Lower heat if chicken begins to brown too quickly. 

Slice chicken crosswise. 

Divide cheesy arepas between plates. Fan chicken next to arepas. Drizzle everything with crema. Top with tomato, cilantro, and as much pickled onion as you like (draining first). Squeeze remaining lime wedges over the top. Serve.