It's German Leberkäse, it's finely ground meats poured into a thing then oven baked, it's generally not something you'd sit down at a fancy restaurant to eat, but rather get at a food truck like thus.
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It's good eating really, you can pan fry them, they come in fine like above, more coarse, even with things added, the pizza variant is popular, it has cheese and bell pepper added in the meat mass.
As I said, nobody's sitting down at a restaurant though to get something like that, that's got to be a tourist trap, there's no reason to get it over something like a proper steak or schnitzel, nor would anybody put mustard on a fucking pretzel. They don't even have proper salt and pepper shakers I'm fairly sure I've seen those disposable mills at a German Aldi at some point. Any reasonable person would have paid about a buck fifty for his meal, he probably threw down a twenty of Lynne's money.