Preheat your oven to 375°F (190°C). Grease the muffin tin with butter or cooking spray.

Melt 3 tablespoons of butter in a medium saucepan over medium heat. Whisk in 3 tablespoons of all-purpose flour to create a roux.

Gradually whisk in 1 cup of chicken broth and ½ cup of heavy cream, stirring until smooth and thickened, about 3-5 minutes.

Remove from heat and stir in 2 cups of cooked chicken and 1 cup of frozen mixed vegetables. Season with salt, pepper, garlic powder, and onion powder.

On a floured surface, roll out the puff pastry and cut circles about 4 inches in diameter.

Press each pastry circle into the greased muffin tin, ensuring the edges extend above the rim.

Spoon the chicken and vegetable filling into the pastry-lined muffin cups, filling about three-quarters full.

Cut circles for the tops of the muffins from the remaining pastry and place them on top of the filled cups, pressing the edges to seal.

Bake for 25-30 minutes or until the pastry is golden brown and the filling is bubbling.

Cool for about 5-10 minutes before serving. Use a butter knife to gently release the muffins from the tin.