Heat a large cast iron skillet over medium-high heat until slightly smoking.
Add the avocado oil to the hot pan, followed by the halved mushrooms in a single layer.
Sear undisturbed for 3 full minutes to develop a thick, brown crust on the bottom.
Toss the mushrooms, reduce the heat to medium, and pour in the balsamic vinegar, soy sauce, smoked paprika, salt, and pepper.
Cook for 2 more minutes until the liquid reduces to a sticky glaze.
Stir in the butter and minced garlic during the final minute of cooking, tossing until fragrant. Garnish with fresh parsley before serving.
