Preheat oven to 180° C. Spray silicone muffin tray with cooking spray. Line the muffin holes with pastry with some left above the rim. (I use a cookie cutter with the same diameter as my muffin hole to line the bottom then cut a wide strip of pastry to line corners.)
Peel, core and dice apples. Place diced apples with 1 tsp cinnamon and a tablespoon of water in a sauce pan and bring to a simmer for a few minutes or until the apple starts to soften. (I purposely leave out the sugar in the apple stewing since my crumble mixture and pastry are already sweet). Remove pan from heat and allow to cool. Drain excess water.
To make the crumble topping, start by cutting the butter into small cubes. Add flour, sugar, oats and 1 tsp cinnamon then mix to form a coarse, crumbly mixture.
Scoop the apple into the muffin tray until full. Sprinkle crumble mix over the apples.
Bake apple crumble muffins in a preheated 180°C oven for around 25-30 minutes or until the pastry and the topping is golden. Carefully remove the apple crumble muffins from the silicone tray while still warm.
Best served warm with a scoop of vanilla ice cream or fresh whipped cream.