01 - In a medium mixing bowl, combine sirloin cubes with olive oil, salt, black pepper, and smoked paprika. Toss thoroughly to coat, and let stand at room temperature while preparing remaining ingredients.
02 - Heat olive oil in a large skillet over medium-high heat. Add quartered baby potatoes, season with salt and black pepper. Cook, stirring occasionally, until golden brown and fork-tender, about 12 to 15 minutes. Remove potatoes from the skillet and keep warm.
03 - Increase skillet heat to high. Arrange marinated steak cubes in a single layer (work in batches if necessary). Sear for 2 minutes without stirring, then turn and continue cooking another 2 to 3 minutes until well browned and cooked to preferred doneness. Transfer steak bites to a plate and set aside.
04 - Reduce heat to medium. Melt unsalted butter in the same skillet. Add minced garlic and thyme (if using); sauté, stirring constantly, for about 30 seconds until aromatic.
05 - Return cooked potatoes and steak bites to the skillet. Toss ingredients in the garlic butter until evenly coated and thoroughly heated, about 1 to 2 minutes.
06 - Sprinkle with freshly chopped parsley and serve immediately.