Pre heat the oven to 475 F. Line a baking sheet with parchment paper and set aside. In a small bowl mix 4 garlic cloves, smashed, olive oil and dry thyme and combine well.
Place diced potatoes and the olive mix in a zip bag seal then mix well to coat evenly.
Spread potatoes in the prepared baking sheet, then sprinkle salt and pepper to taste (I found a pinch of each works great). Make sure you don't over crowd the potatoes as they will boil instead of roasting so use a large baking sheet.
Place in the pre heated oven and roast for 25-30 minutes or until the potatoes are a golden brown.
Meanwhile, place sliced mushrooms in a non stick skillet, sprinkle salt and pepper to taste, add 3 tbsp olive oil and saute until the mushrooms are slightly soft and brown and the juice has evaporated, about 7-10 minutes. Add minced garlic and saute for an additional minute or until the garlic is fragrant.
Turn the heat off and sprinkle chopped fresh parsley. Mix to coat.
Mix cooked mushrooms with roasted potatoes and serve warm or re heat in the oven for a few minutes, if served the next day.