Butter a 13-by-9-inch baking pan, then line the pan with waxed paper. Extend the paper over the edges of the pan to make the candy easier to remove.
In a heavy saucepan, melt chocolate chips with the sweetened condensed milk and butter. Remove from heat.
In a large bowl, combine nuts and marshmallows. Fold in chocolate mixture.
Spread in waxed-paper-lined 13 by 9 pan.
Cool two hours. Peel off waxed paper, and cut into squares.
Store covered at room temperature.
Each year when I was a child, my Texas grandparents would ship a holiday box filled with the taste of home.
Even when we couldn't be together, I could taste the love in my grandfather's specialty, Rocky Road.