In a small saucepan, combine the maple syrup and the cinnamon over medium heat. Add the apple slices and slowly simmer until the apples are tender. Divide the mixture into 6 greased ramekins.
In a large bowl whisk the eggs and egg yolks. Stir in the vanilla, sugar and milk. Pour this mixture slowly into the ramekins. Cover each ramekin tightly with foil.
Fill the pressure cooker with 2 1/2 cups water. Place as many ramekins as will fit on a cooking rack or basket and lower into the cooker onto the trivet. (Note: you can stack the ramekins in a pyramid to fit inside the cooker). Close the lid and bring to pressure.
Lock lid in place and bring to HIGH pressure. Stabilize and cook for 6 minutes.
When done, let the pressure drop naturally, and keep the lid closed for 10 minutes. Then remove the lid, take out the basket, loosen the foil on each ramekin, and cool the flan to room temperature.
Refrigerate the ramekins to cool. Serve once cooled with a drizzle of maple syrup over each ramekin if desired.