Lightly grease the inside of a 5- to 6-quart slow cooker with butter or nonstick cooking spray. This helps prevent sticking and makes serving easier.
Cut the bread into evenly sized cubes. Brioche, challah, French bread, or sturdy white bread works well. If the bread is fresh and very soft, leave it uncovered for a short time to dry slightly.
Place the bread cubes into the prepared slow cooker. Sprinkle the white chocolate chips or chopped white chocolate evenly between the bread cubes, reserving a small amount for the topping if desired.
In a large mixing bowl, whisk together the eggs, milk, heavy cream, sugar, melted butter, vanilla extract, salt, and optional cinnamon. Continue mixing until the eggs are fully incorporated and the sugar begins to dissolve.
Pour the custard mixture evenly over the bread and white chocolate. Gently press the bread down with a spoon so that the cubes absorb the liquid. Let the mixture stand for approximately 5–10 minutes.
Sprinkle the reserved white chocolate over the top. If you enjoy a subtle citrus flavor, add a small amount of finely grated lemon zest before cooking.
Cover the slow cooker and cook on LOW for approximately 2½–3½ hours. Cooking times vary by appliance, so begin checking around the 2½-hour mark.The pudding is ready when the center is set, the bread is tender, and no visibly liquid egg custard remains. For food safety, the center should reach 160°F (71°C).Avoid lifting the lid repeatedly because this releases heat and can extend the cooking time. Switch off the slow cooker and allow the pudding to rest for 10–15 minutes. This helps the custard settle and makes serving easier.Spoon the warm pudding into bowls. Add whipped cream, fresh berries, white chocolate shavings, or a drizzle of melted white chocolate for an elegant finish.