Grilled Chicken:
Coat the chicken tenders in seasonings and olive oil.
Heat a pan over medium-high heat.
Cook the chicken tenders until cooked through and lightly seared (~4 minutes per side). Avoid overcooking.
Rest the tenders for 5 minutes, then chop into cubes, tossing them in the juices. Set aside.
Spinach Alfredo Sauce:
Melt butter in a non-stick pan over medium-high heat.
Sauté chopped onion until softened (~3-5 minutes).
Add garlic and spices; cook for 1-2 minutes until fragrant.
Stir in flour and cook for 1 minute.
Pour in milk and cream, then reduce heat to low. Stir continuously until the sauce thickens slightly.
Turn off the heat, stir in spinach and Parmesan, and adjust seasoning as needed.
Assembly:
Preheat oven to 350°F (175°C) and line 2 baking sheets with parchment paper.
Slice each sheet of rolls into halves, creating 4 “flatbread” sheets (do not separate the rolls).
Toast the bread in the oven for ~8 minutes until lightly golden.
Spread the spinach alfredo sauce over the toasted bread.
Sprinkle half of the shredded mozzarella, then evenly distribute the grilled chicken.
Top with remaining mozzarella and sliced red onion.
Switch the oven to broil (500°F with top grill). Broil for ~5-8 minutes until the cheese melts and turns golden.
Slice, serve, and enjoy!