Preheat the oven to 400°F (200°C). On a large rimmed baking sheet, spread 8 cups of tortilla chips in an even single layer or slight overlap so they cover most of the sheet but don't create a thick mound. Lightly brush or spray the chips with 1 tablespoon vegetable oil (or spray) and sprinkle with 1/2 teaspoon coarse salt.

Bake the chips for 3–5 minutes until just starting to crisp and warm. Remove from oven and set aside. (This step helps ensure chips stay crisp under toppings.)

Blackened chicken

Season and cook chicken

Slice the chicken breast into 1/2-inch strips or bite-sized pieces so it cooks quickly. Toss the chicken with 1 tablespoon blackening seasoning and 1 teaspoon olive oil to coat evenly.

Heat a 10-inch skillet over medium-high heat until hot. Add the seasoned chicken in a single layer and cook 3–4 minutes per side (total 6–8 minutes) until blackened on the outside and internal temperature reaches 165°F (74°C). Remove to a plate and let rest 2 minutes, then chop into bite-sized pieces if needed.

Fresh toppings

Prepare fresh ingredients

While the chicken cooks, dice the tomato to yield about 1 cup, finely chop 1/2 cup red onion, thinly slice 2 jalapeños (remove seeds if you prefer milder heat), and chop 1/4 cup fresh cilantro. Cut 2 lime wedges for serving.

Cheese & sauce

Make creamy cheddar sauce

In a small saucepan over medium heat, melt 1 tablespoon butter. Whisk in 1 teaspoon flour and cook 30 seconds to form a roux. Gradually whisk in 1/2 cup cream until smooth. Bring to a gentle simmer, reduce heat to low, and stir in 2 cups shredded sharp cheddar a handful at a time until fully melted and smooth. Season with 1/4 teaspoon salt and 1/8 teaspoon black pepper. Keep warm on the lowest heat, stirring occasionally. If sauce is too thick, thin with 1–2 tablespoons water or more cream.

If you prefer to skip the sauce, reserve shredded cheddar to be layered directly on chips and melted in the oven.

Assemble & bake

Layer the nachos

Reduce oven to 375°F (190°C). On the prepared sheet of warmed chips, scatter half of the warm cheese sauce evenly over the chips (or sprinkle half the shredded cheddar), then distribute half the cooked blackened chicken, half the diced tomato, half the red onion, and half the sliced jalapeños. Repeat with remaining chips (or top remaining chips already on sheet) by drizzling the rest of the cheese sauce (or sprinkling remaining shredded cheese), remaining chicken and remaining fresh toppings so toppings are evenly spread.

Bake in the 375°F oven for 5–8 minutes, until cheese is fully melted and toppings are warmed. Keep an eye so chips don't burn.

Finishes & garnish

Finish and serve

Remove nachos from oven. Dollop 1/2 cup sour cream in several spoonfuls across the tray or place in a small bowl for serving. Pit and dice 1 avocado; either fan slices over the top or add diced avocado scattered across the nachos. Garnish with 1/4 cup chopped cilantro and optional 2 tablespoons pickled jalapeños. Squeeze lime wedges over as desired and serve immediately.

Leftovers: store assembled but uneaten components separately (chips will lose crispness). Reheat chicken and cheese sauce, then reassemble quickly before serving.