Start by lining your 9x13 inch baking pan with parchment paper, allowing some overhang on the edges. This will make it easier to lift out your Rocky Road once it’s set.
In a double boiler or microwave-safe bowl, combine the chunks of butter and semi-sweet baking chocolate. If using a microwave, heat in 30-second intervals, stirring in between until melted and smooth.
Once your chocolate and butter mixture is melted and well combined, remove from heat. Stir in the vanilla extract for that extra layer of flavor.
Gently fold in the quartered large marshmallows and chopped walnuts (if using) into the chocolate mixture. Make sure everything is evenly coated.
Carefully pour the mixture into your prepared baking pan. Use the spatula to spread it evenly.
Refrigerate the pan for at least 2 hours, or until the Rocky Road is firm enough to cut into squares.
Once set, use the overhanging parchment paper to lift your Rocky Road out of the pan. Cut into squares and serve to your eager friends and family!
