To poach the chicken, place it in a saucepan and cover with water. Bring the water to a boil, then lower the heat and let it simmer for 10-12 minutes, or until the chicken's internal temperature reaches 165°F (74°C). I recommend using a kitchen thermometer to avoid overcooking, as that can make the chicken dry.

Move the chicken to a cutting board or bowl, then shred it using two forks. In a skillet, heat some oil and sauté the onion for about 3 minutes, until it becomes soft and translucent.

Add the garlic to the skillet and sauté for 30 seconds. Then, stir in the cumin, oregano, chili powder, and salt, cooking for another minute. Pour in the salsa, mix it well, and add a splash of water if needed. Let the mixture warm through.

Add the shredded chicken to the skillet and stir it into the sauce. Let it simmer for 2-3 minutes to absorb the flavors.

Serve the chicken mixture in warmed tortillas or taco shells, and top with your favorite toppings.