Preheat the oven to 400 F.
In a large bowl, make the steak’s marinade while combining olive oil, balsamic vinegar, spices and chopped garlic.
Place portobellos and asparagus in an oven-safe skillet. With a pastry brush, generously brush the marinade on the tops and bottoms of both mushrooms and asparagus. Set mushrooms top side down and place the remaining marinade over them. Bake for 20 minutes. Remove from oven, flip, and bake another 5-10 minutes until mushrooms are cooked all the way through.
Wash and peel potatoes. Bring them to boil until they are tender. Mashed them using a potato masher or a hand blender (I choose this one because it provides with extra softness). Add olive oil, black pepper and salt to taste. In the end, add fresh herbs.
For a juicy result, serve immediately.