Preheat oven to 350°F. Line a large baking sheet pan with parchment paper.
Peel banana, break into chunks, and place in a medium bowl.
1 banana
Add sugar, oil, and vanilla to the bowl with the banana. Crush with a fork or potato masher until smooth.
½ cup brown sugar
2 tbsp virgin coconut oil
1 tsp vanilla extract
Roughly chop walnuts. Add to the bowl along with the coconut; stir to combine.
⅔ cup walnuts
⅔ cup shredded unsweetened coconut
Place flour, cocoa powder, cornstarch, baking powder, baking soda, and salt in a small bowl; stir to combine.
½ cup all-purpose flour
2 tbsp cocoa powder
½ tsp cornstarch
¼ tsp baking powder
¼ tsp baking soda
⅛ tsp salt
Add flour mixture to the bowl with the banana and stir to combine the cookie batter.
Using a scant ¼-cup measure, divide batter into 8 portions and place on the baking sheet. Using a rubber spatula or the back of a spoon, spread each cookie into a 2-inch circle.
Place baking sheet in the oven and bake until cookies are slightly firm around the edges, about 15 minutes. Remove from oven and let cool to room temperature.
Once cool, arrange half the cookies on a flat surface, bottom-side facing up. Place a scoop of ice cream on top of each, then cover with remaining cookies. Gently press cookies into the ice cream to secure the sandwiches.
12 fl oz (1 ½ cups) vanilla ice cream
To serve, divide ice cream sandwiches between plates and enjoy!