Heat the olive oil in a 12-inch cast-iron skillet over medium-high heat. Once heated, add the tri-tip and saute until browned, 3 to 4 minutes. Add the garlic, shallot and mushrooms, then season with salt and pepper and saute until softened, about 3 minutes. Add the spinach and cook until wilted, about 1 minute. Add the egg yolks, if using, and quickly stir to cook through. Stir in the Parmesan. Taste for seasoning and serve hot garnished with more Parmesan. Eat with spoons.