Preheat oven to 350 degrees F.
In a large bowl, with an electric mixer, cream together the peanut butter and brown sugar for about 1 minute. Then add in the vanilla extract and maple syrup and mix again until combined.
In a medium sized bowl add the oat flour, baking powder, and salt. Mix until combined.
Slowly add the flour mixture to the peanut butter mixture in two batches and mix until everything is combined. Add the almond milk and mix again. Add the mini chocolate chips and gently mix into the cookie dough with a spoon or you can use your hand.
Divide the cookie dough in half. Line a 9x13 inch baking dish with parchment paper and press in half of the dough mixture. You want the cookie dough to cover the entire pan in a thin layer.
Place the pan into the oven and bake for 12 minutes. The cookie dough may seem underdone, but it will firm up a little as it cools and then it will firm up even more when you freeze it. Lift the cookie dough out of the pan by the parchment paper and set on a cooling rack.
Repeat the same process for the 2nd half of the cookie dough. Let ice cream sandwich cookies cool.
Banana Ice Cream: Cut the bananas into small pieces and freeze for at least 2 hours.
Add the soaked cashews to a blender with ¼ cup of almond milk. Blend for about 30 seconds - 1 minutes, until it has a creamy texture.
Next, add the frozen bananas, maple syrup, and 1 /2 cup almond milk and blend until you get a creamy mixture, about 2 - 3 minutes. You may have to adjust the bananas as you go and mix it up to make sure the blades can get to all the bananas.
Ice Cream Sandwiches: Line the 9x13 inch pan with parchment paper. Carefully flip the peanut butter sandwich cookie upside down (this step isn't necessary, but it will make the top look better). Slowly slide the cookie onto the parchment paper. Top with the banana ice cream and spread around evenly. Carefully slide the second piece of peanut butter cookie on top of the ice cream.
Place ice cream sandwiches into the freezer and freeze for at least 2 hours. When ready to eat, slice into desired ice cream bar sizes.