Apple Filling

• Make the caramel apple filling first because it needs time to cool down. Peel 4 large apples (about 1000g before being peeled and cored), remove the cores, and cut them into small pieces (roughly 1 cm cubes).
• Add the apple pieces, 1/2 cup unsalted butter, 1 1/2 cups packed light brown sugar, 1 tsp cinnamon, and 1/4 tsp salt into a large skillet. Heat over medium-high heat, and stir occasionally. Cook until the mixture begins to bubble, then reduce the heat to medium.
• In a small bowl, whisk together 1/4 cup of water and 1/4 cup of cornstarch to make a cornstarch slurry. This will help thicken the filing. Pour into the apple mixture and cook for 5-10 more minutes, stirring occasionally. Cook just until the apples are soft - I like to test them with a fork!
• Transfer the filling into a large bowl or tray (the wider it is, the faster it'll cool down) and chill in the fridge. Once fully cooled, the filling can be stored in the fridge in an airtight container for up to a week (it doesn't freeze well). Be sure the filling has reached room temperature and thickened before you use it.