Prep

1. Shred Chicken using fork, using two if needed. Shreds should be about 1/4 to 1/3 inch thick.
2. Dice onion.  Chop Avocado into squares. To do this, cut in half and remove pit using Avocado tool. Peel off skin and cut flesh into chunks in cross-cross fashion.  Rinse Chipotle peppers. Pop them open to rinse away seeds.  Chop cilantro and add to sour cream. Stir and place in fridge.

Cook

1. Heat saute pan (affiliate) over medium heat and add olive oil.  When warm, add chopped onion and cook for 3 minutes, until translucent.  Add garlic and cook 1 minute more. Toss in chipotle peppers, cumin and oregano. Toast for 1 minute.
2. Pour in chicken stock, fire roasted diced tomatoes and salt. Reduce heat to simmer and cook for 5-6 minutes, until sauce begins to thicken. Remove pan from heat and pour sauce into blender (affiliate). Pulse about 10 times, then switch blender (affiliate) to medium setting and let it go for about 45 seconds, until smooth.
3. Return saute pan (affiliate) to burner and place on medium low. Add chicken and sauce in pan and stir together well. Cook until warmed through, about 4-5 minutes.  Tip: Taste, if it's too spicy add a dollop of sour cream to the mix. Stir and cook over low heat for 1-2 minutes.
4. To serve, place baked tostada on plate. Top with warm chicken mixture. Dollop a spoonful of cilantro sour cream and add crumbled mexican cheese and diced avocados over top.  Finish with a small pinch of fresh cilantro and a squeeze of lime juice. Serve hot!