Using Sauté (normal/medium) on your Instant Pot or a frying pan, cook the leeks until just starting to soften, then add the mushrooms
Add the garlic and cook for 1 more minute.
Mix the corn flour with a little vegetable stock to form a smooth slurry. Pour the cornflour mixture, remaining stock and oatly cream into the sautéed vegetables.
Pick the thyme from the woody stems and add this to the pie filling.
Mix in the Dijon, and season to taste with salt and pepper.
Spoon the filling into a suitable size dish to fit in your Air Fryer. Unroll your defrosted pastry, then cut a circle big enough to cover your pie.
Place your pastry circle on top of your filling and crimp the edges to the pie dish to seal everything together.
Poke a few small holes in the centre of the pie to allow the steam to escape, then brush the pastry with a little oat milk. Place the pie into the basket of your air fryer.
Select Air Fry, set the time to 25 Minutes and the temperature to 170°C.
Once cooked, remove the pie from the Vortex and serve immediately alongside your sides of choice.