Preheat your oven to 400°F (200°C) and lightly grease a muffin tin.

Melt butter in a skillet over medium heat, add diced onion and minced garlic, sauté until translucent.

Add diced chicken and mixed vegetables, cook until chicken is no longer pink, about 5-7 minutes.

Pour in chicken broth and heavy cream, season with dried thyme, salt, and pepper, simmer for 5 minutes.

Roll out puff pastry sheets on a floured surface and cut into squares.

Press pastry squares into muffin tin cups to create a shell.

Fill each pastry cup with the creamy chicken and vegetable filling.

Cover with more pastry squares, pressing edges to seal, and brush tops with beaten egg.

Bake for 25-30 minutes until pastry is golden brown.

Cool for 5 minutes before serving warm.