Step 1

Heat the oven to 325ºF. Meanwhile, melt 2 tablespoons of the unsalted butter in a large oven-safe or cast iron skillet over medium-high heat. Add 1 pound halved baby potatoes, 1/2 teaspoon onion powder, 1/4 teaspoon of the kosher salt, and 1/4 teaspoon black pepper. Toss to combine, then arrange the potatoes cut-side down in a single layer. Cook undisturbed until beginning to brown on the bottom, 1 to 2 minutes.

Step 2

Continue to cook, stirring occasionally, until well-browned and starting to soften, about 4 minutes. Turn off the heat. Transfer the potatoes to a rimmed baking sheet and arrange into a single layer. Place the baking sheet into the oven.

Step 3

Wipe out the skillet. Melt 1 tablespoon of the unsalted butter in the skillet over medium-high heat. Add 1 1/2 pounds sirloin steak cubes in a single layer and season with the remaining 3/4 teaspoon kosher salt. Cook, flipping occasionally, until most of the sides are browned and the steak is just cooked through, 4 to 5 minutes.

Step 4

Reduce the heat to low. Stir in the remaining 1 tablespoon unsalted butter, 4 minced garlic cloves, and 1/2 teaspoon coarsely chopped fresh thyme leaves. Turn off the heat.

Step 5

Transfer the potatoes to the skillet and toss to combine. Garnish with 2 tablespoons coarsely chopped fresh parsley leaves if desired.