1. To make the brown bread crumbs, preheat the oven to 350ºF (180ºC).
2. Crumble the bread into small, bite-sized bits. The largest should be no bigger than a kernel of corn.
3. In a skillet, heat the butter until it melts, then continue to cook until it starts to brown. Remove from heat and stir in the bread bits, 1/2 cup (100g) sugar, cinnamon, and salt.
4. Spread on the baking sheet and cook for 20 to 30 minutes, stirring a few times during baking, until the bread bits are well-toasted; a deep, dark brown.
5. Cool completely then store in an air-tight container until ready to use. (They can be made a few days in advance and stored at room temperature.)
6. To make the ice cream, heat the milk, 1/2 cup (125ml) of heavy cream, sugar and salt in a saucepan.
7. Pour the remaining 1 cup cream (250 ml) into a medium-sized bowl and the cubes or cream cheese or sour cream. Set a mesh strainer over the top and set the bowl in an ice bath.
7. In a separate bowl, stir together the egg yolks. Gradually pour some of the warm milk mixture into the yolks, whisking constantly as you pour. Scrape the warmed yolks and milk back into the saucepan.
8. Cook over low heat, stirring constantly and scraping the bottom with a heat-resistant spatula, until the custard thickens enough to coat the spatula.
9. Strain the custard into the heavy cream and cream cheese (or sour cream) and stir until smooth. Stir in the vanilla and whiskey, if using.
10. Refrigerate until thoroughly chilled, preferably overnight, then freeze in your ice cream maker according to the manufacturer’s instructions. Once churned, quickly fold in about two-thirds of the brown bread crumbs, or as much as to your liking, then store the ice cream in the freezer until firm and ready to serve.