Begin by generously seasoning the steak pieces with salt, black pepper, and red pepper flakes if using. Ensure each piece is well-coated with the spices.
Preheat a large skillet over medium-high heat until hot. Pour in the avocado oil, then place the seasoned steak bites in a single layer. Allow them to sear for 3-4 minutes until they develop a rich brown crust, stirring occasionally. Depending on the size of your skillet, you might need to cook the steak in batches. Once browned, remove the steak from the skillet.
Drain any excess moisture from the skillet. Add the butter or ghee to the pan, allowing it to melt. Then, introduce the minced garlic, sautéing it for about 1 minute until fragrant.
Return the browned steak bites to the skillet, stirring them in the buttery garlic sauce. Cook for an additional 1-2 minutes, ensuring the steak is thoroughly coated with the sauce. Remove the skillet from the heat and mix in the chopped parsley. Garnish with sliced green onion before serving. Enjoy immediately.