Place 1/3 cup of the walnuts in a food processor fitted with a metal blade.
Process the walnuts until they resemble coarse sand.
Transfer the processed walnuts to a small bowl and set aside for coating the brownie balls.
Add the remaining walnuts to the food processor.
Process until the walnuts are finely ground.
Add the pitted Medjool dates, pumpkin purée, cocoa powder, sea salt, and vanilla extract to the food processor.
Process until the ingredients are fully combined and the mixture becomes smooth, thick, and sticky.
Stop the food processor as needed and scrape down the sides to ensure the mixture blends evenly.
Check the texture of the mixture. It should hold together when pressed between your fingers.
Using a spoon or clean hands, divide the mixture into 8 equal portions.
Roll each portion into a ball, approximately golf-ball size.
Roll each ball in the reserved processed walnuts until evenly coated.
Serve immediately, or place the brownie balls in an airtight container.
Store in the refrigerator or freezer until ready to serve.