Step 1

Bring smashed garlic, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, and 3 cups water to a simmer in a medium saucepan over medium heat. Add mussels and cook, uncovered, until opened, about 3 minutes. As mussels open, use tongs to transfer them to a medium bowl; discard any mussels that remain closed after 5 minutes or so. Chill mussels 15 minutes.

Step 2

Meanwhile, stir grated garlic, tomato, chile, onion, lime juice, 2 Tbsp. cilantro, and remaining ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt in a small bowl.

Step 3

Remove and discard top shells from mussels. Arrange mussels on a platter; top each with a spoonful of salsa. Scatter cilantro sprigs over.