01 - Preheat the oven to 350°F. Grease an 8x8-inch baking dish with butter.
02 - Place the cinnamon roll bread cubes evenly in the baking dish. If using, sprinkle raisins or sultanas between layers.
03 - In a large bowl, whisk together eggs, granulated sugar, vanilla extract, cinnamon, nutmeg, and salt until well combined.
04 - Add whole milk and heavy cream to the egg mixture, whisking until the custard is smooth.
05 - Pour the custard evenly over the bread cubes, pressing gently to ensure full absorption. Allow to rest for 10 minutes.
06 - Dot the surface with softened butter and sprinkle with demerara sugar if desired for extra crunch.
07 - Bake in the preheated oven for 35 to 40 minutes until the custard is set and the top is golden brown.
08 - Remove from oven and cool slightly. Dust with powdered sugar and serve warm.