Step 1: Prepare the Grilled Chicken

1. Coat the chicken tenders in the seasonings and olive oil.
2. Heat a pan over medium-high heat and cook the chicken for about 4 minutes per side, until lightly seared and fully cooked.
3. Rest the chicken for 5 minutes, then chop into small cubes. Toss the cubes on the chopping board to absorb the juices. Set aside.

Step 2: Make the Spinach Alfredo Sauce

4. Melt butter in a non-stick pan over medium-high heat.
5. Add the chopped onion and sauté for 3-5 minutes until soft.
6. Stir in the garlic, salt, black pepper, chili flakes, and Italian seasoning. Cook for 1-2 minutes until fragrant.
7. Add the flour and cook for 1 minute, stirring continuously.
8. Slowly pour in the milk and cream, then reduce heat to low. Stir until the sauce thickens slightly (about 3 minutes).
9. Remove from heat, then stir in the chopped spinach and Parmesan cheese. Taste and adjust seasoning if needed.

Step 3: Assemble the Flatbread

10. Preheat oven to 350°F (175°C) and line 2 baking sheets with parchment paper.
11. Slice the Hawaiian sweet rolls into four large flatbread sheets, keeping them intact. Place on baking sheets.
12. Toast in the oven for 8 minutes, until lightly golden. Remove from the oven.
13. Spread the spinach Alfredo sauce evenly over the toasted bread.
14. Sprinkle over half the mozzarella, then add the chopped grilled chicken.
15. Top with the remaining mozzarella and thinly sliced red onion.

Step 4: Bake & Serve

16. Switch the oven to broil/grill setting (500°F / 260°C).
17. Place the flatbread in the oven and broil for 5-8 minutes, until the cheese is melted and golden brown.
18. Slice and serve immediately. Enjoy!