Preheat your oven to 425°F (220°C).

In a medium bowl, whisk together the maple syrup, white miso, rice vinegar, and soy sauce until smooth. Stir in the water until well combined.

In a large bowl, toss the sweet potato rounds with 1 Tbsp. of neutral oil and 1/2 tsp. of kosher salt until they are evenly coated.

Heat 1 Tbsp. of oil in a large ovenproof skillet over medium-high heat. Add the sweet potatoes in a single layer and cook undisturbed until golden brown on the bottom, about 2 to 3 minutes.

Carefully flip the potatoes. Sprinkle the remaining 1 tsp. of kosher salt on the second side, then cook undisturbed for an additional 1 to 2 minutes until nicely golden.

Add the unsalted butter to the skillet. Once it melts and starts frothing, tilt the pan and use a large spoon to baste the melted butter over the potatoes for about 30 seconds.

Pour the maple-miso glaze into the skillet around the potatoes, bringing it to a gentle simmer.

Transfer the skillet to the preheated oven. Roast until the potatoes are tender and the glaze has reduced to a syrupy consistency, about 23 to 28 minutes.

Carefully transfer the melting sweet potatoes to a platter. Whisk the remaining sauce in the pan and drizzle it over the potatoes. Optionally, sprinkle with flaky sea salt before serving.