Step 1

In a large skillet, melt butter over medium heat. Add onion, carrot, celery, thyme, salt and pepper, cooking for 5 to 6 minutes or until vegetables are tender.

Step 2

Sprinkle flour over the vegetables and cook, stirring, for 1 minute. Gradually whisk in milk and chicken broth. Stirring constantly, cook for 8 to 10 minutes or until mixture begins to simmer and thickens. Stir in broccoli, chicken, mustard and nutmeg; return to simmer. Remove from heat and stir in 1 1/2 cups of the cheese.

Step 3

Preheat oven to 425F.

Step 4

Divide filling among six 1-cup ramekins; let cool slightly. Place pastry on lightly-floured surface and cut into six equal squares. Place one piece of pastry atop each ramekin, pressing gently to adhere. Beat egg with 1 tbsp water and brush lightly over the pastry. Cut two steam vents in the centre of each pie. Sprinkle the remaining cheese on top of the puff pastry.

Step 5

Place ramekins on a parchment-lined baking sheet. Bake for 20 minutes, or until filling is bubbling and pastry is golden brown. Let stand for 5 minutes before serving.