Generously butter an 8-inch square pan.

In a medium, heavy-bottomed saucepan, combine 1 1/4 cups heavy cream and 2 cups unsalted butter. Heat over medium heat until melted. Set aside.

In a separate, heavy-bottomed saucepan over medium heat, melt 2 cups granulated sugar. Use a candy thermometer to monitor the temperature constantly until the sugar reaches 300 (F).

When the sugar reaches 300 (F), ladle a small amount of the cream and butter mixture (from the 2nd step) to the caramelized sugar. It will boil and sputter violently, but this is normal. Continue ladling the cream and butter mixture into the sugar until completely combined; heat the mixture to 260 (F), before adding 5 ounces finely chopped dark chocolate, using a heatproof rubber spatula to stir the mixture until it is a uniform golden-brown color.

When the caramel has cooled completely, slice the caramels into square or rectangular shapes. Transfer the caramels to a sheet of wax paper. Prepare a wire rack by placing over a baking sheet (this will catch any excess chocolate and salt that fall off the caramels).

Set aside about one-third of the 8 ounces of finely chopped chocolate. Place the remaining two-thirds of chocolate in a double boiler, or a heatproof glass or metal bowl set over a saucepan full of simmering water (if doing the latter, make sue the bottom of the bowl does not touch the water). Allow the chocolate to melt, stirring occasionally and monitoring the temperature with a candy thermometer.

When the chocolate has fully melted and reached just above 105 (F), remove the pot (or bowl) from heat. Dry the bottom of the pot (or bowl) with a dish towel, before stirring in the reserved chocolate (from the 2nd step). Stir until the chocolate temperature drops between 88 - 90 (F).

Carefully remove any unmelted pieces of chocolate and set aside. Test the temper by smearing a small amount of chocolate on wax paper, and allowing it to cool at room temperature for about 10 minutes. The chocolate should feel dry, with a smooth, streak-free and shiny finish. If the chocolate appears dull or streaky, you can melt the chocolate and repeat the tempering process.