Ingredients:
Mayonnaise
2 tablespoons grated white onion
1 ripe Hass avocado, pitted and peeled
2 tablespoons mayonnaise
2 plum tomatoes, cored, seeded, and chopped
1 tablespoon finely chopped fresh cilantro leaves
2 teaspoons fresh lime juice
1 small garlic clove, grated
Kosher salt
2 poblano chile peppers
1-1/2 pounds ground chuck (80% lean)
1-1/2 teaspoons kosher salt
1 teaspoon ground black pepper
4 hamburger buns

Directions:

  • Using a sieve, rinse the grated onion under cold water and let the excess water drain off.
  • In a medium bowl, mash the avocado and mayonnaise together with a fork.
  • Stir in the onion, tomatoes, cilantro, lime juice, and garlic.
  • Season generously with salt.
  • Cover with plastic wrap, pressing the wrap directly onto the surface, and set aside. (The mayonnaise can be prepared up to 8 hours ahead.)
  • Prepare the grill for direct cooking over high heat (450° to 550°F).
  • Brush the cooking grates clean.
  • Grill the chiles over direct high heat, with the lid closed as much as possible, until the skin is blackened on all sides, about 10 minutes, turning occasionally.
  • Transfer the chiles to a bowl and cover with plastic wrap to trap the skin.
  • Let stand for about 10 minutes.
  • Remove the chiles from the bowl and peel off and discard the blackened skin, stems, and seeds.
  • Chop the chiles into 1/2-inch dice.
  • In a large bowl gently mix the ground chuck, chiles, salt, and pepper, and shape into four patties of equal size and thickness, about 3/4 inch thick.
  • With your thumb or the back of a spoon, make a shallow indentation about 1 inch wide in the center of each patty so the centers are about 1/2 inch thick. This will help the patties cook evenly and prevent them from puffing on the grill.
  • Grill the patties over direct high heat, with the lid closed as much as possible, until cooked to medium doneness, 8 to 10 minutes, turning once when the patties release easily from the grate without sticking.
  • During the last minute of cooking time, toast the buns, cut side down, over direct heat.
  • Top the burgers with the mayonnaise and serve warm.