Prepare a rimmed baking sheet with a silicone mat, tin foil or parchment paper and set aside. Try and make sure your baking sheet or area you are pouring onto is about 9x11 inches or the equivalent.
Get out all of your decorations and have them ready to add on top of your chocolate once your chocolate is melted and hasn't hardened yet. The chocolate will cool off fast and you need to be ready!
In a non stick skillet or heavy bottomed saucepan, heat butter, sugar, and salt over medium heat, stirring frequently or constantly, for at least 10 minutes. Just preparing you for what lies ahead!
Mixture will continue to gently boil or simmer and remember to keep stirring.
The temperature will gradually increase and reach between 290 and 300 degrees or turns a light brown golden color. I usually remove candy when it is 290 degrees because at that point the temperature continues to increase faster than I move and I don't want to burn it!
Once mixture turns brown, and is almost 300 degrees, quickly fold in chopped nuts and then pour on to your prepared rimmed baking sheet.
Sprinkle chocolate and white chips over the top, in a generous even layer, then let it sit for a few minutes.
Using a spatula or a silicone tool, spread melted chocolate chips all over your toffee, smooth the chocolate right out, and add sprinkles or whatever decorations you are using.
Refrigerate for 2-3 hours, then break into squares and enjoy.