Step 1

Blend shallots, lemongrass, chiles, ½ cup sugar, 2 Tbsp. fish sauce, and 2 Tbsp. oil in a blender until smooth. Season lamb chops generously with salt; place in a baking dish. Pour marinade over chops; turn to coat. Cover and chill 2 hours, then let sit at room temperature 30 minutes.

Step 2

Prepare a grill for high indirect heat (for a charcoal grill, bank coals on one side of grill; for a gas grill, leave one or two burners off); oil grate. Scrape excess marinade from lamb; grill over direct heat, turning every minute or so and moving to indirect heat as needed, until deeply browned and an instant-read thermometer inserted into thickest part registers 130° for medium-rare, 6–8 minutes. Transfer to a platter and let rest 5 minutes.

Step 3

Meanwhile, whisk lime juice, garlic, ginger, remaining ½ tsp. sugar, and ¼ tsp. fish sauce in a medium bowl until sugar is dissolved. Gradually drizzle in remaining 2 Tbsp. oil, whisking until emulsified; season dressing with salt. Add arugula and pear to bowl; toss to coat.

Step 4

Serve lamb chops with salad.