Bring a 1-2 cups of water to a boil in a medium pot fitted with a steamer basket. Place sweet potatoes in the steamer. Cover, reduce heat to medium, and steam until potatoes are completely tender, 35 to 40 minutes.

While the potatoes are cooking, whisk butter, tahini, lime juice, soy sauce, sesame oil and garlic in a medium bowl until smooth. Taste, and season with salt, pepper and lime juice as needed.

Set a small pan over medium heat. Add sesame seeds, and toast, stirring continuously until seeds are golden. We suggest stirring with a wooden spoon to keep the seeds moving, as they may give off oil and start to clump. Once toasted, about 4 minutes, transfer seeds to a small bowl.

When the sweet potatoes are tender, use tongs to transfer them to a large plate. Once cool, split potatoes in half lengthwise, and season with flaky salt. Spread tahini butter generously onto the potatoes, and top with toasted sesame seeds.

Add lime wedges for garnish, and serve hot.