Frontier Fudge

Combine butter, evaporated milk, and sugar in a large heavy-bottomed saucepan over medium heat, stirring frequently until the mixture reaches a rolling boil.

Boil the mixture for exactly 5 minutes, stirring constantly to prevent scorching on the bottom and sides of the pan.

Remove the saucepan from heat and immediately add the unsweetened chocolate, semisweet chocolate chips, and milk chocolate, stirring until completely melted and smooth.

Fold in the large marshmallows, stirring gently until they are fully incorporated and the mixture is creamy.

Stir in the vanilla extract until evenly distributed throughout the fudge mixture.

Fold in the chopped walnuts or pecans until well distributed, being careful not to overmix.

Pour the fudge into a buttered or parchment-lined 9x13-inch baking pan, spreading it evenly with a spatula.

Allow the fudge to cool at room temperature for 30 minutes, then refrigerate for at least 2 hours until firm enough to cut.

Cut the cooled fudge into 1-inch squares using a sharp knife, wiping the blade between cuts for clean edges.

Store the fudge in an airtight container at room temperature for up to 2 weeks, or in the refrigerator for extended freshness.