Put the chopped chocolate, condensed milk, salt and butter in a heavy bottom pan on low heat. Stir to melt.
Put the nuts in a ziplock bag and bash them with a rolling pin, to get coarse pieces.
Add the broken nuts to the chocolate mixture. Stir well. Remove from flame.
Pour the mixture into a 10X6 inch tray. Spatch and smooth the top.
Allow the fudge to cool to room temperature. Using a knife, gently mark the fudge with the grid of lines - depending on how small or big pieces you want.
Move the tray to refrigerator to set. This will take about 15-20 minutes.
Once set, remove from refrigerator and just gently snap-break on the lines you had made earlier.
These can be stored in freezer and eaten straight out without thawing.