Bring the vegetable stock to a gentle boil, then add the barley and butter, then reduce to low heat.
Cover and cook for 10 minutes, then turn off the heat and let it sit, covered, for another 5 more minutes.
Meanwhile, heat the garlic olive oil in a pan and sauté the shallots until softened. Add the mushrooms with a pinch of salt to help release moisture and cook until water evaporates. Stir in the sun-dried tomatoes, followed by the spinach, and cook until wilted. Add the garlic, and once fragrant, pour in the wine and stock, allowing it to cook for a minute. Add the grated zucchini and squash, stirring to combine.
Once the barley is ready, fold it into the vegetable mixture. Stir in the Parmesan cheese, butter, and cream, allowing everything to meld and thicken slightly.
Adjust seasoning with salt and pepper, garnish with a drizzle of Truffle Oil if desired, and serve hot. Enjoy!
