Heat oil in a deep pot or Dutch oven over medium-high heat until shimmery. Place chicken in a single layer and let it begin to brown for several minutes.

Meanwhile, coarsely chop the tomatoes, jalapeño and garlic and put into a small pot with salt and water. Cover and bring to boil. Boil 3-4 minutes until soft. Turn off heat and add ketchup, oregano and pepper. Blend to puree. Be careful when blending hot liquids and be sure to hold the lid of the blender down with a towel over it.

Once chicken is browned on one side, flip it and add the salsa and cover. Bring to simmer  and simmer 25-30 minutes until tender. Shred chicken in the pot. I use a pair of tongs to squeeze it apart. Increase heat to high and fry the meat until the salsa thickens and the chicken gets some crispy bits.