In a small saucepan over low heat, melt the butter. Add minced garlic and cook until fragrant, about 2 minutes. Remove from heat, then stir in olive oil, thyme, and parsley. Let it cool slightly.

Place steak cubes in a large bowl. Pour half of the garlic butter marinade over the steak, reserving the rest. Toss to coat the steak evenly. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.

Thread marinated steak cubes and mushrooms onto skewers, alternating between the two. Season with salt and pepper to taste.

Prepare your grill by preheating it to medium-high heat. Ensure the grill is clean and well-oiled to prevent sticking.

Place the skewers on the grill and cook for 8-10 minutes, turning occasionally, until the steak is cooked to your desired doneness. Baste with the remaining marinade throughout the grilling process.

Remove skewers from the grill and let them rest for a few minutes. Drizzle any remaining garlic butter over the skewers before serving.

Remove the steak and mushrooms from the skewers and store in an airtight container in the refrigerator for up to 3 days.

To reheat, place in a preheated oven at 350°F for 10 minutes, or heat in a skillet over medium heat with a little butter.