Preheat oven to 200 degrees celsius (fan-forced).
Place the pastry sheets onto the bench and allow to defrost.
Place the leeks, garlic and bacon into the Thermomix bowl. Chop for 3 seconds on Speed 5.
Add the butter and saute for 5 minutes, Varoma, Reverse, Speed Soft (Stir).
Add the chopped chicken and cook for a further 5 minutes, Varoma, Reverse, Speed Soft (Stir).
Add the cooking cream and chicken stock and cook for 20 minutes, 100 degrees, Reverse, Speed Soft (Stir).TIP: If the sauce has not thickened enough, mix 1 tbs cornflour with ¼ cup water. Add to the Themomix bowl and mix for 20 seconds, Reverse, Speed Soft (Stir).
Lightly grease a 12 hole muffin tray.
Use a small bowl or cutter (approximately 13cm in diameter) to cut 12 circles from the shortcrust pastry sheets (2 per sheet).
Use your fingers to press them into the muffin tray holes (each pastry round should be large enough to slightly overhang).TIP: Cut a small triangle section out from each pastry circle as this helps when fitting them into the muffin holes.
Divide the mixture equally between the 12 muffin tray holes (being sure not to over-fill).
Cut 12 slightly smaller rounds (approximately 10cm in diameter) from the puff pastry sheets (4 per sheet).
Place them over the top of the meat pies and use your fingers to seal the overhanging shortcrust pastry to the puff pastry top.
Brush over the whisked egg and sprinkle with sesame seeds.
Bake for 25 minutes or until golden.