a 13-by18-inch rimmed baking sheet with the 1 tablespoon softened butter, making sure to grease the corners of the pan. Set the prepared baking sheet aside on a heat-safe surface, like a large wood cutting board.
Place the remaining 1 pound butter, sugar and 1 teaspoon of the sea salt in a cast-iron skillet set over high heat and whisk
occasionally until the butter melts. Reduce the heat to medium-high and cook, whisking frequently, until the mixture has slightly thickened and is tan in color, about 20 minutes. Insert a candy thermometer into the mixture and continue to cook while whisking constantly until the mixture has reached 305 degrees F (the hard crack stage), about 10 minutes.
Using thick oven mitts (the pan will be extremely hot) immediately pour the hot mixture into the prepared baking sheet, tilting it to get an even layer. (Note: Hot sugar syrup
will burn and stick to your skin; be careful when pouring to avoid splattering.) Cool the buttercrunch until it is slightly set but still soft, about 5 minutes. Using a knife or bench scraper, score the buttercrunch into 1-inch squares. The score marks will close up while the mixture is still hot, so just keep making the score
marks until they remain in place, then let the buttercrunch cool completely, about 1 hour. Break the buttercrunch into pieces along the score lines and place the pieces in a bowl.
While the buttercrunch cools, toast the walnuts: Preheat the oven to 250 degrees F.
Spread the walnuts on a baking sheet and toast them, stirring occasionally, until golden brown and fragrant and the skins are starting to flake, about 45 minutes. Remove the walnuts from the oven and set them aside to cool completely. Place the walnuts
in a food processor
until coarsely chopped. Transfer the chopped nuts to a medium bowl and sprinkle the remaining 2 teaspoons of salt over them, tossing to combine.
While the nuts toast, temper the chocolate: Bring a saucepan filled with 1 inch of water to a simmer
over medium heat. Reduce the heat to low, add 1 1/2 cups of milk chocolate and 1 1/2 cups of dark chocolate
to a large heat-safe bowl, and set it over the hot water (make sure the bottom of the bowl does not touch the simmering water). Melt
the chocolate, stirring often, until completely smooth (you can also melt the chopped chocolate in a microwave-safe bowl at 50 percent power, stirring every 1 1/2 minutes until the chocolate is completely melted, 4 to 6 minutes). Remove the chocolate from the saucepan
. Off the heat, stir in the remaining chopped milk and dark chocolate a little at a time until the chocolate being added no longer melts into the mass. Once this happens, the chocolate is tempered.
Line a large baking sheet with wax or parchment paper. Set the 3 bowls side-by-side: buttercrunch, chocolate and then the walnuts. Set a spider skimmer next to the bowls with a pair of long tweezers (or chopsticks). Drop a few pieces of the buttercrunch into the chocolate. Use the skimmer to submerge them, then use the skimmer to scoop and lift the buttercrunch out of the chocolate, tapping the skimmer handle on the rim of the bowl a couple of times to drain
the excess chocolate. While holding the chocolate in the spider, use your other hand and the tweezers to transfer the chocolate-coated pieces of buttercrunch in the bowl of walnuts. Set the pieces in one by one, and take care so they dont touch one another. Gently sprinkle the walnuts over the dipped buttercrunch pieces to cover them completely, then carefully transfer them to the prepared baking sheet to set completely, about 20 minutes. Repeat with the remaining pieces of buttercrunch.
The Buttercrunch Toffee
can be stored in an airtight container at cool room temperature (approximately 65 degrees F.), for up to 2 weeks or in the refrigerator for up to 1 month.