Wash and dry all produce. Preheat oven to 450 degrees. Halve each zucchini lengthwise, then scoop out seedy cores with a spoon; discard cores. Place on a lightly oiled baking sheet and rub with a drizzle of olive oil. Season with salt and pepper. Arrange cut-side down, then roast in oven until tender and browned on bottom, 20-25 minutes.

Meanwhile, bring 1 cup water and stock concentrate to a boil in a small pot. Add quinoa, then cover, lower heat, and reduce to a simmer. Cook until tender, 15-20 minutes.

Trim, then finely chop mushrooms. Peel and mince shallot. Mince or grate garlic. Finely dice tomatoes. Strip thyme leaves from stems; discard stems. Finely chop leaves.

Melt 1 TBSP butter in a large pan over medium heat. Add shallot and cook, tossing, until soft, 2-3 minutes. Add 1 TBSP olive oil, mushrooms, tomatoes, and thyme to pan. Cook until very soft, 5-6 minutes. Toss in garlic and cook until fragrant, 30 seconds. Season with salt and pepper. Once quinoa is done, add to pan and toss to combine. Season with salt and pepper.

Remove zucchini from oven once they are finished roasting. Heat broiler to high or increase oven temperature to 500 degrees. Stuff zucchini with as much filling as will fit (you will have some remaining). Sprinkle with Parmesan. Broil or bake until Parmesan is melted and starting to crisp, 2-3 minutes.

While zucchini is in oven, chop parsley. Divide remaining filling between plates. Place stuffed zucchini on top once finished broiling. Garnish with parsley and serve.