Combine butter, oil, onion, garlic, and mushrooms and cook down on medium heat until onions are clear. Be careful to not scorch the garlic. This is best done in the pan used to cook the meat.
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Recipe
Rouladen is a classic German dish that tantalizes the taste buds with its rich flavors and tender texture. Thinly sliced beef is rolled around a savory filling of mustard, bacon, onions, and pickles, then braised to perfection in a robust gravy, creating a hearty and satisfying meal typically enjoyed with mashed potatoes or red cabbage.