Begin by placing a medium saucepan over low heat. Combine the semisweet chocolate chips, sweetened condensed milk, and butter. Stir continuously for 5–7 minutes until melted and silky smooth.

Remove from heat and stir in the vanilla extract and salt. If adding nuts, fold them in for extra texture.

Line an 8-inch square baking dish with parchment paper. Ensure the parchment covers the bottom and sides completely.

Pour the warm fudge mixture into the dish and spread it out evenly. Add festive sprinkles if desired.

Chill in the refrigerator for at least 2 hours until fully set.

Lift the fudge out using the parchment overhang, place on a cutting board, and cut into squares.