Line a half sheet pan with foil.
Combine the first 4 ingredients in a large bowl and stir until the are evenly mixed.
Put the sugar, milk, cream, butter, and salt in a heavy bottom pan and heat over medium low, stirring occasionally, until the mixture comes together and the sugar dissolves. Test this by rubbing a bit of the mixture between your finger tips to see if you can feel any sugar.
Once the sugar is dissolved, turn the heat up to medium high and bring to a boil. Turn down to just above medium and cook, stirring slowly once in a while, until the mixture reaches 230 on a candy thermometer or instant read. This takes about 15 minutes.
Immediately when it hits 230, pour over the mixture in the bowl. Don't scrap the pan, just dump it and start stirring. Stir vigorously until the chocolate melts and the mixture is thickened and smooth. Don't over mix because you need to pour into the pan while it is still smooth.
Pour into the foil lined pan and smooth the top a bit. Top with the chocolate chips if you are using them. Allow to cool slightly then place in the fridge to fully set up.
Cut into desired size pieces. Can be stored in an airtight container in the fridge for up to a month. Can also be stored in the freezer.