Line 8" or 9" square baking dish with parchment paper
Add about 2 or 3 inches of water to the bottom of a medium saucepan then place the heat resistant bowl over top just above the water. Ensure that edges of bowl are tight up against the saucepan because you do not want any water to splash into the bowl. Water will cause the chocolate to seize. Bring water to a simmer over medium-low heat.
Add 3 cups of semi-sweet chocolate, and the 14 oz can of sweetened condensed milk. Mix until chocolate is melted, smooth and combined with the condensed milk.
Add a pinch of salt and 1 1/2 tsp of vanilla and mix well.
Remove from heat at pour into prepared baking dish. Press down gently till fudge is even and pushed into every edge of the pan. Cover with plastic wrap in cool in the refrigerator for 2 hours.
When cooled lift the parchment paper with fudge out of the baking dish and peel away the parchment paper. Cut into squares and serve. Store covered in the fridge for up to 2 weeks. Fudge becomes softer at room temperature.
Nutrition based on adding 3/4 cup of walnuts to the recipe.