• Line a sheet pan with parchment paper. Set aside.

Make the Dough:

• In a medium mixing bowl, whisk together the flour, baking soda, baking powder, cinnamon, and salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, add the butter, coconut oil, maple syrup, and dark brown sugar. Mixing on medium, cream together until pale tan and fluffy, 2-3 minutes. Add in the vanilla, egg, and egg yolk. Mix until combined.
• Working in increments, slowly add the dry ingredients into the wet, mixing on low until just combined. Remove the paddle attachment, cover the bowl with clingwrap, and set aside.

Make the the Cinnamon Filling:

• In a small bowl, mix together the brown sugar, butter, and cinnamon until totally combined and smooth.

Assemble and Chill:

• Using a cookie scoop, scoop out 20 tablespoon-sized cookies onto the prepared sheet pan. Don’t worry if the sheet looks crowded, this is only to chill them, not to bake. Top each of the dough balls with a small, ½ teaspoon of the cinnamon filling in the middle of the ball. Finally, with the remaining cookie dough, scoop another 20 directly atop the existing cookies, making a sandwich.
• Using your fingers, gently press down atop each cookie to flatten. The cinnamon layer may squeeze out the sides a bit, but it should mostly remain within the cookie.
• Transfer the baking sheet to the freezer and chill for at least an hour, or overnight.

Bake the Cookies:

• Preheat the oven to 350℉. Line two baking sheets with parchment paper.
• Divide your dough between each tray, leaving ample space between them. You may need to bake in batches! Transfer to the oven and bake for 12-14 minutes, rotating the trays halfway through.
• Remove from the oven, and bang the sheet pan on the counter to flatten the cookies slightly. See note for an extra tip for perfectly shaped cookies! Transfer the cookies to a wire rack and repeat with the remaining cookies.

Make the Icing Glaze and Frost:

• Allow the cookies to cool entirely. While the cookies are cooling, mix together the icing. In a medium mixing bowl, add the powdered sugar, cinnamon, kosher salt, and almond milk. Whisk until smooth and totally combined.
• Add about 2 teaspoons of icing to each cookie, using a spoon to smooth the icing out, leaving about a 1-centimeter border around the edges. Allow to set before storing.