Line an 8x8-inch square baking dish with aluminum foil.
In a medium saucepan, melt the semi-sweet chocolate chips and sweetened condensed milk together over low heat, stirring constantly to prevent burning. Once the chocolate is just melted, remove from the heat and continue stirring until the mixture is completely smooth and velvety.
Remove the pan from the heat and stir in the vanilla extract and a pinch of salt. Stir in 1 cup of the chopped walnuts until evenly distributed throughout the chocolate mixture.
1 teaspoon Vanilla, Pinch of Salt, 1 1/2 cup Chopped Walnuts
Pour the fudge mixture into the prepared baking dish, spreading it out evenly with a spatula. Smooth the top and sprinkle the remaining walnuts over the top, pressing them in gently.
Place the fudge in the refrigerator and let it set for at least 2 hours or overnight. Once set, remove it from the pan and cut it into small squares.
Notes
Storage: This fudge will stay fresh for up to a week when stored in an airtight container at room temperature, in the fridge for 30 days, or in the freezer for up to 3 months. Be sure to wrap the fudge in plastic wrap before storing it in the freezer.
Make it festive: For a holiday twist, sprinkle some sea salt, or drizzle melted white chocolate over the top before chilling.
High-quality ingredients: Use a chocolate chip like Ghiradelli for the best results.