Chicken Tinga and Avocado Tostadas

Heat the oil in a casserole or large heavy-bottomed pan over medium heat. Once hot, add the onion and cook until soft and translucent, 4 to 5 minutes. Add the garlic and cook until it becomes fragrant, less than a minute.

Add the crushed tomatoes, adobo sauce, dash, oregano, marjoram, thyme, and black pepper. Bring to a simmer, cover partially and cook, stirring occasionally, until the sauce thickens and darkens, about 10 to 12 minutes.

Incorporate the shredded chicken broth and the chicken broth into the sauce and toss until well mixed. Cook, stirring occasionally, until the chicken has absorbed almost all of the sauce and is moist but not runny, about 8 minutes more. Remove from heat.

Place the tostadas on a platter. Top with a generous amount of chicken tinga, a couple tablespoons shredded lettuce, and 1/4 of a ripe avocado.