Heat your oven to 350. Line 2 baking sheets with parchment paper. Set aside.

In a small bowl, mix the flax with 6 tbsp. warm water, stir well, set aside.

In a large bowl, combine the flour, cocoa, salt and baking soda. Set aside.

In a medium saucepan, heat the butter and sugar.

In a high-powered blender, blend the cashews and water. Slowly add the cashew mixture to the butter mixture, stirring well. Add the flax mixture and peanut butter, and stir until combined.

Slowly add the liquid mixture to the flour mixture, 1/2 cup at a time, until fully combined. Fold in the oats, walnuts, and chocolate chips.

Scoop the cookie batter onto the prepared baking sheets, into 1" balls, flatten gently. Bake at 350 for 16 minutes, remove from the oven, and cool completely.

Make the icing: using a hand mixer, combine the peanut butter with the powdered sugar, 1/2 cup at a time. Add in the vanilla, and then the almond milk, adding 1 tsp. at a time until desired consistency.

When the cookies are cool, ice the bottoms of the cookies with the peanut butter frosting. Form into sandwiches, and enjoy!