In a large saucepan over medium heat, melt butter. Stir in flour and cook, stirring constantly, about 2 minutes. Slowly whisk in stock until you have a smooth sauce.

Bring to a boil and add sweetpotatoes, chicken, scallions, peas, thyme, salt and pepper. Cook on low, stirring frequently until sweetpotatoes are tender, 6-10 minutes. Remove from heat and let cool 5-10 minutes. Divide between 4 medium-sized ovenproof bowls.

Preheat oven to 400 degrees F.

Cut 4 circles from puff pastry, each large enough to cover the top of bowls. Brush rims of bowls with water and place a pastry round on top of each, pressing edges tightly to seal. Brush tops of pastry with egg wash.

Place prepared bowls on a baking sheet. Bake 20 minutes or until puffed and golden-brown.

Let rest 5 minutes before serving.