MAKES 4 SERVINGS

This recipe is based on one in Rosa's New Mexican Table by Roberto Santibañez (Artisan, 2007); it's for the same dish that is prepared at Rosa Mexicano restaurants in New York City. "It is our signature dish—nine out of ten guests order it," says Santibañez. "One of the things that make our guacamole special is that when we opened, in 1984, we were among the first, if not the first, restaurants on either side of the border to serve it prepared tableside in a traditional molcajete [a mortar made from volcanic rock]." We think it's the best guacamole we've ever had.

2 tbsp. finely chopped white onion
3 firmly packed tbsp. chopped fresh cilantro
2 tsp. finely chopped jalapeño
1 tsp. salt
3 medium-ripe hass avocados
3 tbsp. diced tomato

1. Grind 1 tbsp. of the onions, 1 tbsp. of  the cilantro, jalapeño, and salt together in a molcajete until all the ingredients are well ground. (Alternatively, use a fork to mash the ingredients to a paste in a wide bowl.)

2. Cut avocados (about 8 ounces each) in half. Twist the halves to separate them and remove the pit with the tip of the knife. Place an avocado half, cut side up, in your palm and make 3 or 4 evenly spaced lengthwise cuts through its flesh down to the skin, without cutting through the skin. Make 4 crosswise cuts in the same fashion.

3. Scoop the diced avocado flesh into the molcajete. Repeat with remaining avocado halves. Gently fold the avocado into the chile–onion paste, keeping the avocado pieces fairly intact.

4. Add tomatoes, remaining 2 tbsp. of the cilantro, and remaining 1 tbsp. of the onions.

5. Fold together all the ingredients. Taste and add salt, if necessary.

6. Serve immediately, directly from the molcajete (or bowl), with tortilla chips.