Heat olive oil in a large skillet over medium heat. Add finely chopped onion and red bell pepper, sauté for 3-5 minutes until softened. Add the cooked and finely diced or shredded chicken, garlic powder, dried oregano, red pepper flakes (if using), salt, and black pepper. Stir well and cook for another 2 minutes.

Reduce heat to low. Add the softened cream cheese, shredded cheddar cheese, and grated Parmesan cheese to the skillet. Stir continuously until all cheeses are melted and the mixture is well combined and creamy. Remove from heat and let cool slightly.

Unroll the crescent roll dough on a clean, lightly floured surface or parchment paper. If using crescent rolls, separate them into triangles. If using puff pastry, gently unfold it. For crescent rolls, pinch seams together to form a rectangle, then cut into approximately 16 squares (about 3x3 inches each). If using puff pastry, roll it slightly thinner and cut into 16 squares.

Place a small spoonful (about 1-1.5 tablespoons) of the chicken filling in the center of each dough square.

Fold one corner of the dough over the filling to meet the opposite corner, forming a triangle. Pinch and seal the edges tightly with your fingers or a fork to prevent the filling from escaping during baking. Repeat with remaining dough and filling.

In a small bowl, whisk together the egg and water to create an egg wash. Place the assembled mini chicken pockets on a baking sheet lined with parchment paper (for oven) or directly into the air fryer basket (ensure they don't touch). Brush the tops of each pocket with the egg wash and sprinkle with sesame seeds, if desired.

Preheat oven to 375°F (190°C). Bake for 15-18 minutes, or until golden brown and puffed.

Preheat air fryer to 350°F (175°C). Air fry in batches for 10-12 minutes, flipping halfway through, or until golden brown and puffed. Cooking time may vary depending on your air fryer model.

Allow the Mini Chicken Pockets to cool for a few minutes before serving. They are best served warm.