In a food processor combine walnuts and 1/8 tsp. salt. Cover and pulse until finely chopped. Transfer to a shallow dish.
In food processor combine dates, cocoa powder, apple juice, and 1/4 tsp. salt. Cover and process until mixture forms a thick paste, adding 3 to 4 tsp. water if necessary, 1 tsp. at a time, to reach desired consistency.
Using 2 tsp. of the dough for each truffle, shape into a ball. Roll balls in walnuts to coat. (If dough becomes too sticky, chill 15 to 20 minutes). If desired, dust with cocoa powder. Cover and chill at least 1 hour before serving. Store in refrigerator up to 2 weeks.