Step 1

First, make the puff pastry: in a small bowl, stir together the flour and salt. Add the diced butter, and use a pastry blender, fork or your fingers to smear the butter into the flour mixture. It should be homogeneous and the butter should be in pieces about the size of peas, with some bigger.

Step 2

Next, add 2 tablespoons of water and stir gently with a fork to bring the dough together. If it seems overly dry, add the final tablespoon of water.

Step 3

Wrap the dough in plastic and refrigerate until ready to use.

Step 4

Preheat the oven to 425.

Step 5

In a small saucepan, make the filling: add the butter to the pan and let it melt. Add the chopped vegetables and saute (while stirring occasionally) for about 5 minutes.

Step 6

Sprinkle the flour over the vegetables, and cook for 30 seconds while stirring.

Step 7

Add the stock, milk, thyme, salt and pepper. Let this mixture come to a simmer. Taste and adjust for seasoning.

Step 8

Finally, stir the cooked chicken into the mixture and remove from the heat.

Step 9

Ladle the chicken filling mixture into desired serving dish.

Step 10

Remove the pastry from the fridge, cut it half, and roughly roll out to cover the serving dish. It's best if the filling doesn't touch the pastry, but it's totally fine if it does.

Step 11

Beat the egg yolk, and brush it over the crust.

Step 12

Bake for 15-19 minutes, until the filling is bubbling and the crust is golden brown.

Step 13

Remove from the oven and let cool for a few minutes before serving.