1. Preheat your oven to 375 F (190 C). Lightly grease a 9×13-inch baking dish with butter or non-stick cooking spray.

2. Cut the sourdough discard focaccia into roughly 1-inch cubes. Place the cubes in a large mixing bowl.

3. In a small microwave-safe bowl, melt the unsalted butter. In a separate small bowl, combine the granulated sugar and ground cinnamon. Pour the melted butter over the focaccia cubes in the large bowl and toss gently to coat. Then, sprinkle the cinnamon-sugar mixture over the buttered focaccia and toss again until all the cubes are evenly coated.

4. Transfer the coated focaccia cubes into your prepared baking dish, spreading them out in an even layer.

5. In a small saucepan over medium heat, combine the brown sugar, heavy cream, vanilla extract, and a pinch of salt. Stir constantly until the brown sugar is fully dissolved and the mixture comes to a gentle simmer. Cook for 1-2 minutes, stirring, until it thickens slightly.

6. Carefully pour the warm caramel sauce evenly over the focaccia cubes in the baking dish. Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the focaccia is golden brown, puffed up, and the sauce is bubbly and caramelized.

7. While the casserole is baking, prepare the glaze. In a small bowl, whisk together the powdered sugar, milk (or heavy cream), and vanilla extract until smooth and pourable. Add more milk a teaspoon at a time if it’s too thick, or more powdered sugar if it’s too thin.

8. Once the casserole is out of the oven, let it cool for about 5-10 minutes. Drizzle the prepared glaze generously over the warm casserole. Serve immediately while it’s still warm and gooey.