Grease a muffin tin with cooking spray. Cut 12 circles with a cutter or glass tumbler of about 6-7cm and press into the muffin tin.
Mix the chicken, crème fraiche, corn and thyme together. Season with salt and black pepper. Spoon into the pastry cases.
Cut 12 circles of about 5cm, to fit the top of the raw pies. Wet the bottom of the lids with a little water and place on top, pressing the edges down lightly. Cut a slit into the top and brush with egg wash.
Sprinkle with sesame seeds and bake at 170℃ for about 30 minutes or until golden. Cool for 5 minutes before removing from the tin.