Seriously--the easiest, ever!
Step 1: Thaw frozen puff pastry sheet (bought mine at Trader Joe's, because they have all butter pastry sheets).
Step 2: Peel, core, and halve an apple. Cut each half into quarters.
Step 3: Cut 2 4" circles out of the puff pastry sheet. Arrange 4 quarters of apple on each.
Step 4: Dot with a bit of butter, a sprinkle of brown sugar, and some cinnamon if you are so inclined. I was not, mainly because I couldn't find the cinnamon.
Step 5: Bake in a 375 oven until the apples are tender and pastry is risen and browned.
Mine could have used another 5 minutes in the oven, but they just smelled so freaking good. And as long as you keep some puff pastry in your freezer, you can whip this up pretty much anytime, in under 30 minutes.
Next time, I'll try a drizzle of maple syrup on top before baking.