Add the tomatoes, chipotles, chili powder, garlic cloves, and chicken broth to a food processor or blender. Blend until smooth and set aside.

Heat a large skillet with 1/2 tablespoon olive oil. Brown the chicken on one side before breaking apart and pushing to one side of the pan.

Add the remaining 1/2 tablespoon olive oil and the onion to the other side of the pan. Cook until the onions start to pick up a little color and soften before mixing in with the ground chicken.

Continue mincing until the chicken is fully cooked.

Add the sauce and continue cooking until it thickens, about 6-8 minutes.

Serve on tostadas with refried beans and garnish with queso fresco, cilantro, and pickled onions, if desired.