Take the skin off the bananas and slice them. Freeze overnight in a resealable food storage bag..
Add the frozen bananas and almond milk to a food processor and blend until smooth. Now add peanut butter, cocoa powder, vanilla extract and salt and blend again until smooth.
Spoon the nice-cream into a parchment paper lined freezer safe container - allow the parchment paper to hang over the sides. (Top tip: Set the nice-cream into a larger dish so that the level of it sits at 1.5-2 cm high - when cutting out the rounds of nice-cream later on the thickness will be perfect.) Cover loosely with cling film. Freeze for 2 hours.
Remove the nice-cream from the freezer and then using the overhanging baking paper, lift the frozen nice-cream onto a flat surface. Using a cookie cutter slightly smaller than the cookies, cut out circles of nice-cream. Place the circle onto one cookie and top with another cookie, gently pushing the two together. Repeat until nice-cream or cookies have been used. If necessary, place the nice-cream sandwiches back into the freezer for 15 minutes to set further.
Place the chopped chocolate into a microwave safe bowl. Microwave for 30 seconds, stir and repeat until there are a few small chocolate pieces remaining. Stop microwaving and stir until chocolate is completely melted.
Remove the nice-cream sandwiches from the freezer and individually dip half of each sandwich into the melted chocolate and sprinkle with chopped nuts. The chocolate will harden quite quickly. Place back into the freezer until ready to eat.