Using a sharp knife, cut the potatoes into 2-inch cubes. Add them to a medium bowl and cover with cold water. Swirl the water with your fingers to remove excess starch, then drain well.

In a large pot, add the potatoes and vegetable stock; season with salt. Bring the mixture to a boil, reduce the heat, and gently simmer for 12-15 minutes, until a paring knife can be inserted into the center with little resistance.

Strain the potatoes in a colander, then shake them in the colander vigorously to roughen the edges. Set aside to cool for 20 minutes.

While the potatoes cool, preheat the oven to 400°F (200°C).

In a small saucepan over medium heat, combine the oil, thyme, rosemary, garlic, and a few grinds of black pepper. Cook, stirring and shaking the pan constantly, for about 3 minutes, or until the garlic just begins to turn golden brown. Immediately pour the mixture through a fine-mesh strainer set over a large bowl. Set aside the garlic-herb mixture and infused oil separately.

Transfer the cooled potatoes to a large rimmed baking sheet, spreading them out evenly, then drizzle them with the reserved infused oil. Roast in the preheated oven, undisturbed, for 20 minutes. Turn the potatoes. Continue roasting the potatoes, turning them every 15 minutes, for a total of 1 hour, or until the potatoes are crispy and evenly roasted on all sides.

Transfer the potatoes to a large bowl. Add the reserved garlic-herb mixture and Parmesan; toss to coat. Season with salt and serve immediately.