Preheat the oven to 400° F.

Slice the peeled sweet potatoes into roughly 1-inch thick rounds.

In a small bowl, whisk together the miso and maple syrup. Add the water in increments until no large clumps of miso remain. Set aside.

Heat a heavy bottomed, oven-safe skillet over medium-high heat. Add the avocado oil. When shimmering, sear the sweet potatoes in a single layer for 3-4 minutes or until browned. Use tongs to flip the potatoes and sear for an additional 1-2 minutes on the other side.

Turn off the heat and add the butter, swirling the pan around so it melts. Pour over the miso mixture and lift up each potato so it gets underneath. Transfer the skillet to the oven to bake.

After 15 minutes, use oven mitts and a spoon to tilt the pan and baste the potatoes with the sauce. Return to the oven to bake for another 5-10 minutes or until easily pierced with a fork.

Transfer the sweet potatoes to a serving plate and pour over the remaining sauce, using a spoon to scrape up any caramelized bits. Serve with a generous pinch of flaky sea salt.