Preheat the oven to 375°F/ 190°C. Line a baking sheet with parchment paper or a silicone baking mat.
Frangipane
With a hand mixer or by hand, beat together the butter, sugar, and salt until it's light and fluffy.
Beat in the egg and vanilla until well combined.
Make the pecan flour: add 120g of pecans to a food processor and pulse the pecans until they resemble fine crumbs.
Add the pecan flour and flour into the frangipane and mix until well combined.
Assembly
Slice open each croissant lengthwise, leaving it slightly attached at the end.
Transfer the frangipane to a piping bag fitted with a large round tip (for easy distribution, optional). Pipe a generous amount of frangipane on to one side of each croissant. Be sure to reserve a small amount of frangipane for the top of each croissant.
Place a heaping 3 tbsp. scoop of apple pie filling on top of the frangipane and spread it out into an even layer.
Fold the top half back on top of the croissants, then pipe a line of frangipane on top of each croissant. Use a knife to slightly spread out the frangipane on top.
Press the crushed pecans onto the frangipane on top of each croissant.
Bake the croissants for 10-15 minutes or until the frangipane starts to turn golden brown.
Dust with powdered sugar, serve, and enjoy!
Notes
*or 8 small croissants**You'll only need to make 1/2 of the apple pie filling recipe for these croissants - or you can make the whole batch and freeze the extra for more croissants later on. The apple pie filling can be made in advance and be stored in the fridge for up to 5 days or in the freezer for up to 3 months.