In a small skillet, toast the rice over medium heat, shaking the pan frequently, until the rice is deep golden brown, 15 to 20 minutes.

Transfer to a small bowl. Put the chiles in the now-empty but still-hot skillet and toast them over low heat, turning them frequently until fragrant and dark spots appear, about 1 minute.

Remove the chiles from the skillet and let both the rice and chiles cool completely.

In an electric coffee grinder dedicated to spice-grinding, pulse the toasted rice to a coarse powder, 3 or 4 pulses.

Return the rice to the bowl. Break the stem off the toasted chiles and shake out the seeds; break the pods into small bits and add them to the grinder.

Process the chiles until you have a slightly coarse powder. Tip the chile powder into a second small bowl.

Trim off the bottom of the lemongrass stalk and peel off and discard a couple of the outer layers.

Using the back of the knife blade, give the bulb end of the lemongrass a few good whacks to flatten and bruise it.

Minced the pale green portion of the stalk, sprinkle on the black pepper, and continue to mince until the lemongrass is as fine as you can get it.

Transfer the mixture to a ramekin, add 2 teaspoons of the fish sauce and the oil, and mix to form a paste.

Rub this paste into both sides of the steak, evenly coating it, and refrigerate while you prepare the dressing and heat the grill.

In a small bowl, combine the lime juice, the remaining fish sauce, the sugar, and ½ to 1 teaspoon of the chile powder.

Stir until the sugar dissolves and set the dressing aside.

Build a very hot fire for direct-heat cooking in a charcoal grill or heat a gas grill with all burners on high.

Let the grill grate heat, covered, for about 10 minutes, scrub it clean with a wire brush, and oil it lightly.

Grill the steak until a digital instant-read thermometer inserted into the thickest part registers 120 degrees for rare or 125 degrees for medium-rare.

Transfer the steak to a clean plate and let rest for 5 to 10 minutes while you prepare the shallots.

Slice the shallots into ⅛-inch-thick rings and separate the rings; you should have about 1 cup.

When the steak is rested, cut it with the grain into sections about 2½ inches wide, and then slice each section against the grain into very thin slices.

Toss the steak slices into a medium bowl and pour in any meat juices from the cutting board as well as from the resting plate.

Add the shallot rings, 1 tablespoon of the rice powder, most of the mint and cilantro, and all of the dressing.

Toss to combine, taste and add more fish sauce, if you like, and then transfer to a serving platter.

Sprinkle the remaining mint and cilantro on top and sprinkle with the remaining rice powder. Serve right away, with the rice.