Combine the jalapeño, garlic, and onion chunks in a food processor and pulse until roughly chopped. Add the lime juice, lime zest, olive oil, water, salt, and black pepper, then blend until you have a chunky marinade with visible texture. Place the cubed chicken breasts in a bowl or resealable container, pour the marinade over, and toss to coat evenly. Cover and refrigerate for at least 2 hours (or up to 8 hours for deeper flavor). The acid from the lime juice will gently tenderize the chicken while the aromatics infuse it with bright, complex flavors.
While the chicken marinates, place the thawed spinach in a clean kitchen towel or cheesecloth and squeeze out all excess moisture—this step is crucial to prevent a watery filling and soggy enchiladas. Measure out the shredded jack cheese for the filling, the salsa verde, and the topping cheese so everything is ready to assemble. Chop the fresh cilantro and finely dice the red onion, then set aside for garnish.
Heat a large skillet over medium-high heat. Working in batches to avoid crowding the pan, cook the marinated chicken pieces for 5-7 minutes per side until golden and cooked through (the internal temperature should reach 165°F). I like to let the first side develop a nice golden crust before flipping—this adds deeper flavor to the filling. Transfer the cooked chicken to a cutting board and let it cool for about 10 minutes, then shred it into bite-sized pieces using two forks or your hands.
In a large bowl, mix the shredded chicken from Step 3 with the squeezed dry spinach from Step 2, half of the jack cheese (about 1 1/4 cups), the ground cumin, and the chicken stock. The stock helps keep the filling moist so the enchiladas don't dry out during baking. Stir until well combined and taste for seasoning—adjust salt and pepper if needed. Set the filling aside.
Preheat your oven to 375°F. Warm the tortillas in the microwave (wrapped in a damp paper towel for 30-45 seconds) to make them pliable and easy to roll. Spread about 1/2 cup of the salsa verde evenly across the bottom of a 9x13 inch baking dish. Working with one tortilla at a time, place about 3 tablespoons of the filling mixture from Step 4 down the center, roll it tightly, and place it seam-side down in the prepared dish. Repeat with all tortillas, arranging them snugly in a single layer.
Pour the remaining salsa verde evenly over the rolled enchiladas, then sprinkle the reserved 8 oz of shredded jack cheese over the top. Cover the dish tightly with aluminum foil and bake for 20 minutes. I like to tent the foil loosely rather than sealing it completely—this helps the cheese melt evenly without steaming the tortillas. After 20 minutes, carefully remove the foil and bake uncovered for another 15-20 minutes until the cheese is bubbly and beginning to brown at the edges.
Remove the enchiladas from the oven and let them rest for 5 minutes before serving—this allows the sauce to set slightly and makes plating cleaner. Garnish generously with the fresh cilantro and finely diced red onion from Step 2 for brightness and texture contrast. Serve warm with extra salsa verde and sour cream on the side if desired.
