Line a 4x7-inch baking dish with parchment paper and set aside.

In a mixing bowl, combine the oat flour with the coconut flour. Stir in the maple syrup, coconut oil, and vanilla, and mix until well combined. You should get a soft dough. Press the dough into the baking dish. Top with another layer of parchment paper and press it down firmly using the bottom of a glass. Transfer to the refrigerator while you prepare the pistachio layer.

Add the pistachios, maple syrup, and salt to a food processor and process for 20-30 seconds, or until it has the texture of almond meal. The mixture should be slightly sticky and hold together if you try to shape it into a ball.

Transfer the pistachio mixture into the baking dish, on top of the oat shortbread. Press it firmly into an even layer and refrigerate for 30 minutes.

To make the chocolate ganache, place the chocolate chips (or chopped dark chocolate) in a small bowl, set aside. Heat the almond milk over medium heat in a small saucepan until hot. Pour the hot almond milk into the chocolate chip bowl and let it sit one minute. Next, whisk until the chocolate is melted and fully combined with the milk.

Pour the ganache on top of the pistachio layer and spread it into an even layer. Refrigerate for another hour before cutting into squares.

Pistachio squares will keep in the refrigerator for up to 7 days.