Melt one tbsp of butter and ½ tbsp of olive oil in a cast iron skillet over medium heat.’
Add the potatoes, minced garlic, fresh herbs, red pepper flakes, salt, and pepper and cook them until tender, about 6 minutes. Stir them every few minutes to ensure proper cooking. Transfer to a plate and keep warm.
Using a slotted spoon, discard any pieces of burnt garlic that may have stuck to the bottom of the skillet and melt the remaining butter and olive oil.
Season the sirloin bites with salt and pepper, and add them to the skillet. Do not move them for two minutes so they sear properly.
Continue cooking them until seared on all sides and cooked to your desired level of doneness. Return the potatoes to the skillet.
Cook for an additional minute to heat them through.