Prep:This recipe works best in an 8x8 pan - larger pans make fudge that's thin. Get your ingredients ready.
Prepare pan: Line your pan with foil or with parchment paper; leaving an overhang. Lightly grease with butter and set aside.
Begin melting the chocolate: Place the chocolate chips and sweetened condensed milk in a medium saucepan. Place over medium-low heat and stir constantly until the chocolate is half-melted. Take off the heat.
Finish melting the chocolate: Stir the salt, butter and vanilla into the mixture. Place back over medium-low heat and keep stirring until the chocolate has fully melted and the mixture is smooth and shiny. Immediately take off the heat. Stir in nuts, if using. Note: Do not overcook, or the chocolate will seize up and the fudge will turn out crumbly!
¼ teaspoon salt, 2 tablespoons butter, ½ teaspoon vanilla extract, 1 cup chopped pecans or walnuts
Place in pan: Immediately after taking the fudge off the heat, pour it into your prepared pan. The mixture will be thick. Spread it out evenly into all corners.Note: It looks fun and interesting and delicious if you leave the top of the chocolate a little swirled instead of trying to get it completely smooth!
Set: Let the fudge set completely at room temperature - about 4-6 hours. Cut into squares.Note: You can cut the fudge into 16 larger pieces (4x4 grid as shown in the picture), into 25 medium pieces (5x5 grid) or into 36 small pieces (6x6 grid).