Peel the potatoes. Trim the ends so they are flat, then cut each potato in half crosswise. You should now have 10 flat potato rounds.
Place the potatoes in a large bowl and cover with cold water and let sit for 30 minutes.
Preheat the oven to 400°F and arrange the rack in the middle of the oven.
Drain the potatoes, rinse with cold water, and pat dry with paper towels.
Place them in a dry large bowl and season with the kosher salt, black pepper, paprika, and onion powder.
Add 2 tablespoons of canola oil to a large cast-iron pan over medium-high heat. Once the oil is shimmering, add the potatoes cut-side down in a single layer. Cook until golden brown, about 6 to 7 minutes, flip and cook for 5 more minutes
To the pan next add the garlic, butter, and 4 sprigs thyme, and 4 sprigs rosemary. Stir and cook until the butter is foaming and just starts to brown, 2 minutes.
Add the broth, stir gently and transfer the pan to the oven.
Bake until the potatoes are fork-tender, about 30 to 35 minutes.
Garnish with more fresh thyme and rosemary sprigs before serving, drizzled with the pan juices, and sprinkle parley on top.