Prep the pan: Line an 8-inch square pan with parchment, leaving a sling. Lightly butter the parchment for extra insurance.

Quick Method – Melt and Stir: In a medium saucepan over low heat, combine chocolate chips, sweetened condensed milk, and butter. Stir constantly until mostly melted and glossy. Remove from heat just before fully smooth and keep stirring to finish melting. This keeps it silky and prevents scorching.

Flavor it: Stir in vanilla and salt. Fold in any mix-ins quickly while the fudge is still warm.

Pour and level: Scrape the mixture into the prepared pan. Smooth the top with a spatula. Tap the pan gently on the counter to release air bubbles.

Chill to set: Refrigerate for 2–3 hours, or until firm enough to slice. For best texture, let it sit at room temperature for 10–15 minutes before cutting.

Classic Method – Old-Fashioned Option: In a saucepan, combine sugar, butter, and evaporated milk. Bring to a gentle boil over medium heat, stirring. Boil 4–5 minutes, stirring constantly, until slightly thickened. Remove from heat, add marshmallows and chocolate, and stir until smooth. Stir in vanilla and salt, then pour into the lined pan. Set and slice as above.

Slice cleanly: Use a warm, sharp knife. Wipe the blade between cuts for perfect edges.