Prepare the hash browns: Peel the potatoes, then use a box grater to shred them lengthwise into long strands, then place them immediately into a large bowl of cold water to prevent them from oxidizing. Pour out the water, add a second round of cold water until the shredded potatoes are immersed, and let them sit for about 5 minutes. While the potatoes soak, prepare the crème fraîche: Add crème fraîche, dill and lemon zest to a medium bowl and whisk until aerated, about 1 minute. Season to taste with salt; refrigerate until ready to serve. Strain the potatoes, then use a cheesecloth or towel to squeeze out any excess water (or tightly grip them by the fistful, squeezing any liquid into the sink), transferring potatoes to a large bowl. Season shredded potatoes with the Parmesan, garlic powder, onion powder and a generous amount of kosher salt. (If you notice a little excess water in your bowl, feel free to pour it out.) Mix until everything is incorporated and then shape the mixture into 8 patties, patting them firmly until compact. Once you have your hash browns shaped and ready, divide 3 tablespoons canola oil between 2 large nonstick or cast-iron pans and heat over medium. Gently add 4 hash browns to each pan, using a spatula to sculpt the edges of each hash brown so they’re rounded like hockey pucks. Cook, undisturbed, until golden-brown and crisp underneath, about 5 minutes, reducing the heat to medium-low if browning too quickly. Carefully flip the hash browns, adding about 1 tablespoon of oil to each pan (or more, if needed), and cook over medium until the second side is golden-brown, another 3 to 5 minutes, reducing the heat to medium-low if browning too quickly. Once the hash browns are golden on both sides, working with 1 pan at a time, add 1½ tablespoons butter and 2 thyme sprigs to the pan and cook over medium, tilting the pan slightly and using a spoon to baste the thyme-scented butter over the hash browns, about 1 minute. Turn heat off and transfer butter-basted hash browns to a paper towel-lined baking sheet to absorb any excess oil. Repeat basting step with the remaining hash browns, butter and thyme sprigs. Garnish with chives and serve with crème fraîche.