Preheat oven to 250°F (130°C). In a completely dry 9-inch round cake pan, combine chocolate and salt.
Bake until chocolate is smooth and deep golden and smells like toasted marshmallows, 30 to 60 minutes, stirring every 10 minutes. (At times, the chocolate will look very dry and chalky, but keep stirring until smooth.)
Pour chocolate onto a parchment-lined sheet tray, and let set for at least 7 hours or overnight.
Break into pieces, and store in an airtight container for up to 4 months.
Notes
For a lighter flavor, roast just until color starts to change, about 30 minutes. For a stronger flavor, roast until chocolate resembles peanut butter and has a strong nutty fragrance, about 1 hour. This will produce something slightly less sweet with an assertive caramel flavor.
Recipe by Bake from Scratch at https://bakefromscratch.com/macchiato-chocolate-tart/