In a medium-sized bowl, use a hand mixer to combine coconut oil, maple syrup, vanilla, cinnamon, and salt. Add in all remaining cookie ingredients, except filling. Stir to combine with a spoon, then use your hands to knead the dough for a bit until it forms into a smooth and uniform ball.
Flatten the ball into a disk, place on top of a piece of parchment paper. Cover with a second sheet of parchment and roll out the dough into a ⅛" thickness. Use a 1½” round cookie cutter to cut out the cookies (I used this linzer cutter for mine), but don't lift them off the sheet just yet (they are a little fragile at this point and can easily break). Place the whole parchment sheet onto a cookie sheet and into the fridge or freezer and allow the cookies to chill for about 10 minutes.
In the meantime, preheat the oven to 350F. Line a baking tray with some parchment paper. Once cookies are chilled transfer the cut-out cookies onto the parchment-lined baking tray, spacing them at least an inch apart (they will spread a little as they bake).
Bake for approximately 8 minutes (note: if using larger cookie cutters the baking time will be a few minutes longer). Remove from oven and allow the cookies to cool completely on a rack (they will be soft when you pull them out, but will harden as they cool).
Once completely cool, place less than 1 tbsp dulce de leche into the center of half the cookies. Cover with another cookie and press down to form a sandwich. Repeat. Dust with powdered coconut milk. Enjoy!