Step 1 - Prepare the Chipotle Peppers: Open the can of chipotle peppers in adobo sauce and roughly chop all the peppers. Keep all of the adobo sauce from the can because it adds a lot of flavor to the chicken.
Step 2 - Marinate the Chicken: Place the 3 pounds of boneless, skinless chicken thighs in a large bowl. Add the chopped chipotle peppers along with all of the adobo sauce, 2 pressed garlic cloves, 1¼ teaspoons of salt, 1 teaspoon of ground cumin, and 3 tablespoons of olive oil. Mix everything thoroughly so the chicken is evenly coated with the marinade. Cover the bowl with plastic wrap and refrigerate for at least 2 hours.
Step 3 - Heat the Grill: Once the chicken has finished marinating, grease the grill grates and heat the grill to high heat. Make sure the grill is fully heated before adding the chicken so you can get a good sear while keeping the inside juicy.
Step 4 - Grill the Chicken: Place the marinated chicken thighs on the hot grill. Grill for about 4 to 5 minutes per side, or until the thickest part of the chicken reaches an internal temperature of 165°F. The exact cooking time can vary depending on the thickness of the chicken thighs, so use the internal temperature as your guide.
Step 5 - Rest the Chicken: Transfer the cooked chicken to a plate and loosely cover it with foil. Let the chicken rest for 5 to 10 minutes. This gives the juices time to settle back into the meat and helps keep the chicken juicy when you cut it.
Step 6 - Prepare the Avocado: While the chicken rests, cut the avocado into small cubes, about ½ inch in size. Set the avocado aside until you are ready to assemble the bowls.
Step 7 - Chop the Chicken: Remove the foil from the rested chicken and cut the chicken thighs into small cubes. You can make the pieces larger if you prefer, but small cubes work especially well for a chicken bowl because you get a little chicken in every bite.
Step 8 - Build the Chicken Bowls: Start each bowl with chopped iceberg lettuce. Add the desired amount of chopped chipotle chicken, followed by black beans and cooked brown rice. Spoon your choice of salsa over the top, then add the chopped avocado and finish with sour cream.
Step 9 - Serve: Serve the chicken bowls while the grilled chicken and rice are still warm. Keep the lettuce, avocado, salsa, and sour cream fresh and cool for a good contrast with the smoky chicken.