Preheat the oven to 375°F. Coat a baking dish with 1 tablespoon of the butter.
In a large skillet, cook longaniza, breaking up with a wooden spoon; stir until lightly browned. Add onion, carrots, celery, and garlic and cook over medium heat until onions and celery are wilted and transparent.
Crumble cassava bread into skillet and stir to mix completely. Pour broth over everything and stir so bread soaks up broth. Transfer contents of pan to baking dish. Dot mixture with remaining 1 tablespoon butter. Season with salt and pepper (not much needed, longaniza is highly seasoned). Cover with foil and bake 20 minutes. Uncover and bake another 15 to 20 minutes, until golden and crisp on top.