"Some people call this Rocky Road candy, but our grandma called it Heavenly Hash. Grandma or mom almost always made it for us around Christmas time. Grandma used to wrap each piece individually in plastic wrap, but I'm afraid I don't have that kind of patience. Either way, it looks pretty stacked up on a decorative plate and tastes heavenly as it melts in your mouth. If using a microwave to melt chocolate and butter, stir thoroughly between 30-second bursts until chocolate is completely melted."
Heat chocolate bars, chocolate chips, and butter in the top of a double boiler over simmering water, stirring frequently and scraping down the sides with a rubber spatula to avoid scorching.
Remove chocolate mixture from heat; stir in walnuts, marshmallows, and vanilla until completely coated. Spread mixture into 9x13-inch baking pan, gently pressing down with spatula to evenly flatten out. Refrigerate until hardened, 4 to 5 hours.