Preheat the oven to 375°F (190°C) and grease a 9x13-inch baking dish.
Heat 1 tbsp butter in a skillet over medium-high heat. Sear the cubed steak for 2-3 minutes, seasoning with salt, black pepper, and smoked paprika. Remove from heat and set aside.
In the same skillet, add the remaining butter and sauté onions and garlic until softened.
Layer the casserole: Arrange half of the sliced potatoes in the baking dish. Top with some cheese, half of the steak, and pour in half of the heavy cream and beef broth. Repeat the layers.
Cover with foil and bake for 40 minutes.
Remove the foil and bake for another 15-20 minutes until the cheese is golden and bubbly.
Let it rest for 5 minutes before serving. Garnish with fresh parsley or green onions for a vibrant touch.