Preheat the oven to 350 degrees F (175 degrees C).
Cut tortillas in half and slice crosswise into 1/8-inch strips. Place in a bowl and toss with 1 tablespoon oil until fully coated. Arrange tortilla strips in a single layer on a baking sheet.
Bake in the preheated oven until crisp and light brown, about 15 minutes. Let cool.
Heat remaining oil in a saucepan over medium heat. Add pasilla chiles; cook and stir until light brown, about 4 minutes. Transfer chiles to a plate. Add onion to the saucepan; cook until translucent, about 5 minutes. Add tomatoes; cook until soft, stirring occasionally, about 10 minutes. Reduce heat to medium-low.
Return chiles to the pan; add mint and oregano. Simmer until fragrant, about 3 minutes. Pour in chicken broth, increase heat to medium-high, and bring to a boil. Add chicken bouillon; reduce heat and simmer until flavors meld, about 10 minutes more. Discard mint and oregano. Garnish with the tortilla strips, avocados, and queso fresco.