Scrub sweet potatoes, then chop into cubes a scant 1 in. across.
Warm 1/4 cup oil in a large frying pan over medium-high heat. Add sweet potatoes, turn to coat, and season with a few pinches of sea salt.
Cover pan, turn heat to medium-low, and cook, stirring every now and then, until sweet potatoes are tender and browned, about 20 minutes.
Meanwhile, toast sesame seeds in a frying pan (not nonstick) over medium heat and cook, stirring occasionally, until aromatic and the white seeds are golden.
Serve sweet potatoes drizzled with remaining oil and sprinkled with flaky sea salt and sesame seeds.
*Find at well-stocked grocery stores and natural-foods stores. For flaky sea salt, any kind will work; a good one is buttery Jacobsen sea salt, made in Oregon (jacobsensalt.com).
Make ahead: Chopped raw sweet potatoes, up to 1 day. They don't hold well once cooked--they tend to shrivel--and taste best hot, so make them just before serving.