For the English Toffee:

1. In a large, deep (3 quart) saucepan, melt the butter. Stir in the salt, sugar, water, and corn syrup, and bring the mixture to a boil. Boil gently over medium heat, without stirring, until the mixture reaches hard-crack stage (300°F on an instant-read or candy thermometer; you’ll be taking it off the heat a few degrees sooner). The syrup will bubble without seeming to change much for awhile, but be patient; all of a sudden it will darken, and at that point you need to take its temperature and see if it’s ready. (If you don’t have a thermometer, test a dollop in ice water; it should immediately harden to a brittleness sufficient that you’ll be able to snap it in two, without any bending or softness). This whole process should take about 10 to 12 minutes. Pay attention; too long on the heat, and the syrup will burn.
2. While the sugar is boiling, spread half of the nuts in an even, closely packed layer on a parchment-lined 9″ x 13″ pan. Top the nuts with half the chocolate.
3. When the syrup has reached 295°F, remove from the heat. Pour the syrup quickly and evenly over the nuts and chocolate. Top with the remaining chocolate and let sit for 2 to 3 minutes, until it softens; spread the chocolate with an offset spatula in an even layer and immediately sprinkle the remaining nuts on top.
4. While the candy is still slightly warm, pull it out of the pan and use a thin spatula to loosen it from the parchment. When completely cool, break into chunks.

For the shake:

1. Blend the ice cream and milk together until smooth. Set aside.
   

For the glass decoration (optional):

1. Pour the chopped, toasted peanuts into a wide, shallow dish. Set aside.
2. Melt the cocoa candy melts in a microwave safe bowl, like glass. Microwave for 30 seconds. Stir and microwave again for an additional 30 seconds. Keep stirring and microwaving in short bursts of 15-20 seconds until melted and smooth. Use can alternatively use a double boiler for melting or melt directly in a heat-safe piping bag.
   
3. Dip and coat the outer rim of a glass with the melted candy melts (or if melted in a pastry bag, clip the tip off and pipe the chocolate around the outer edge). Then dip into the chopped peanuts, turning to coat the entire outside rim. Place in the fridge for five minutes to harden.

Assembly:

1. Pour the blended shake mixture into your prepared glass.
2. Spoon or spray whipped cream on top of the shake mixture.
   
3. Place a piece of English toffee in the whipped cream and enjoy!