Begin by buttering 12 small ramekins and dusting with granulated sugar.
Heat the milk and cream in a saucepan over medium heat until steamy (DO NOT BOIL).
Turn off the heat and add the chocolate, salt, vanilla, nutmeg, cinnamon, walnuts and Kahlùa. Stir to mix.
Whisk the egg yolks in a bowl with the 1/2 cup sugar. Pour into the chocolate mixture. Gently fold in the bread cubes.
Transfer the pudding mixture to the ramekins (DO NOT OVER FILL - Fill just to the top) and place on a baking sheet.
Bake until nicely browned and set, about 30 minutes.
Kahlùa Caramel Sauce:
Combine sugar, water and cream of tartar in a small saucepan. DO NOT STIR. Bring the mixture to a boil; cook until the caramel browns. When the caramel is medium brown, remove from heat and add cream. Let simmer. Add Kahlua.
To serve: Ladle some sauce onto each plate, unmold the ramekin, place the pudding on top of the sauce. Serve warm, topped with a scoop of vanilla ice cream.
Cook's Tip: Other serving versions include serving the pudding warm and topped with a dab of whipped cream OR cold, topped with fresh strawberries, whipped cream, and chocolate chips.