Step 1

In a 12-inch skillet over medium, toast the sesame seeds, stirring often, until lightly browned, 2 to 3 minutes. Cool completely, then pulse in an electric spice grinder or grind in a mortar with pestle until fragrant and coarse.

Step 2

In a large bowl, stir together the sesame seeds, mirin, soy sauce, sake, sugar and cayenne (if using). In a 12-inch skillet over medium-high, heat the oil until barely smoking. Add the asparagus and ¼ teaspoon salt, then cook, stirring only a few times, until lightly charred, about 3 minutes.

Step 3

Add 3 tablespoons water, then immediately cover. Reduce to low and cook, stirring just once or twice, until the asparagus is tender-crisp and the pan is dry, 2 to 3 minutes. Add the asparagus to the bowl with the sesame mixture and toss to coat. Taste and season with salt and black pepper, then transfer to a serving dish.