Preheat oven to 320 degrees F (160 degrees C).
Place the New Potato (3 pound) in a greased baking dish. Add Milk (1/2 cup), Heavy Cream (1/2 cup), Ground Nutmeg (1 pinch), Dried Thyme (1/2 teaspoon), Grated Parmesan Cheese (1 ounce),
Season with Kosher Salt (to taste) and Ground White Pepper (to taste) to taste and mix well. Top with Grated Parmesan Cheese (2 ounce) and Unsalted Butter (4 tablespoon). Cover and bake for an hour.
Uncover and continue baking until golden brown and potatoes are cooked through, about 30 minutes.
Once the potatoes are almost done, melt a knob of Butter (to taste) in a pan over medium heat, and sauté the Oyster Mushroom (5) on both sides until golden brown. Season with Kosher Salt (to taste) and Cayenne Pepper (to taste).
Serve the mushrooms and potatoes together.