Preheat your oven to 400°F (200°C) and gather all your ingredients.

In a large skillet, melt 2 tablespoons of butter over medium heat. Add chopped onion and minced garlic, sauté for 3 to 4 minutes until translucent.

Add 1 pound of diced chicken and 2 cups of frozen mixed vegetables to the skillet. Sauté for 5 to 7 minutes until the chicken is cooked through.

Stir in 1 cup of chicken broth and ½ cup of heavy cream, seasoning with salt, pepper, and a sprinkle of dried thyme. Simmer for about 5 minutes until thickened.

Roll out puff pastry sheets on a floured surface and cut into squares that fit a muffin tin. Press into the cups to form bases.

Fill each pastry cup with the chicken filling, and cut smaller pastry squares to cover. Seal edges with a fork and brush with an egg wash.

Bake in the preheated oven for 25 to 30 minutes until pastry is puffed and golden brown.