Preheat your oven to 425℉ degrees.

Heat up your oil in a large saucepan over medium-high heat. Add the mushrooms and leeks and cook until they’re soft (about 4-5 minutes). Add the sweet potato and fresh thyme and cook for another 6 minutes.

Add the flour and stir until the vegetables are evenly coated. Add the stock and use your spoon to scrape up all of the brown bits on the bottom of the pan. Then add the milk and bring the sauce to a boil, stirring constantly.

Let the sauce boil for one minute, then take the pot off the burner. Add the chicken, peas, and salt and let the pot stand for 20 minutes.

Roll out your puff pastry and cut out 4 rounds with the mouth of your ramekin. Fill 4 ramekins with the chicken mixture and top with a pastry puff round. Place the ramekins on a baking sheet and cook until the pastry is golden brown (about 17-19 minutes). Serve warm.