1. Preheat the oven to 400°F and line a baking sheet with parchment paper.

2. Cook the onion and mushrooms in a skillet until softened and most of the moisture has evaporated. Add the garlic and cook briefly, then let the mixture cool.

3. In a bowl, mix the cream cheese, cheddar cheese, Dijon mustard, thyme, black pepper, and salt until combined.

4. Fold in the cooled mushroom mixture and the shredded chicken or turkey if using.

5. Roll out the puff pastry and cut it into even circles. You need two circles for each mini pie.

6. Spoon a small amount of filling into the center of half the pastry circles, leaving a clean border around the edges.

7. Top with the remaining pastry circles, press the edges closed, and crimp with a fork. Cut a small vent in the top of each pie.

8. Brush the tops with beaten egg and chill the pies for 10 minutes.

9. Bake for 18 to 22 minutes, or until puffed and golden brown.

10. Let the pies cool for a few minutes, then top each one with cranberry chutney, onion jam, or sun-dried tomatoes before serving.