Preheat the oven to 330F. Line a baking sheet with parchment paper; set aside.

In a medium skillet over medium heat, melt the butter. Then, add the apple pieces, brown sugar, maple syrup, cinnamon, and apple pie spice. Mix until the apples are coated and the brown sugar is melted. Allow to simmer for 3-5 minutes, until the apples are just slightly cooked and the mixture is glossy. Set aside.

Prepare the simple syrup by heating the sugar and water together in a small pot on the stove, just until the sugar is dissolved into the water. Set aside.

Mix together all of the ingredients for the almond filling in a medium bowl, until well combined. Transfer the mixture to a piping bag or a ziplock baggie with the corner snipped off. Set aside.

Slice the croissants in half, and place them onto the prepared baking sheet.

Brush the bottom half of each croissant generously with the simple syrup. Spoon or pipe half of the almond filling onto the bottom halves of the croissant (reserving the rest of the almond filling for topping).

Divide the apple pie filling among the croissants, placing it on top of the almond filling.

Place the tops on top to close all of the croissants.

Brush the tops of the croissants with more simple syrup. Then, generously spoon or pipe the rest of the almond filling on top, and sprinkle with sliced almonds.

Bake at 330F for 40-45 minutes until they are golden.

Allow to cool slightly.

If using salted caramel: make the salted caramel by combining all of the ingredients together in a small bowl. Mix until smooth.

Dust the croissants with powdered sugar, and drizzle with salted caramel, if desired.