Add the bananas, vanilla and a splash of milk to a food processor. Blend until smooth and creamy, stopping to scrape down the sides of the bowl as needed.
The nice cream will be similar to soft serve at this point. You can eat it as is, or scoop it into a freezer-safe container and freeze it for 2 to 3 hours. This will give you a firmer, scoopable texture.
Make and chill the wet walnuts:
In a small sauce pan over medium heat combine the maple syrup, walnuts, vanilla and salt. Stirring, bring the mixture just to a boil, then remove from heat. Pour the wet walnuts into a bowl and refrigerate until ready to use. *If you need to speed up the cooling process it's also okay to place them in the freezer for a few minutes.
Serving and storage:
Top individual servings of banana ice cream with wet walnuts and enjoy! Leftover wet walnuts can be stored in an airtight container in the refrigerator for up to a month. If the mixture becomes too hard, just place the container in a warm water bath for several minutes or microwave it for a few seconds to soften the syrup.