Place onion, garlic and tomatoes under the broiler, or on an already heated skillet, griddle or comal set over medium heat. Roast or char for about 10 minutes, flipping in between, until ingredients are completely charred, cooked and mushy. Set aside and peel the garlic cloves when cool enough to handle.
In a small skillet set over medium heat, toast the cloves, peppercorns and cinnamon stick for a couple minutes, moving and flipping them around to toast evenly. Set aside. Toast the oregano for 10 to 15 seconds and remove from the heat.
In the jar of a blender, place the charred onion, peeled garlic and charred tomatoes, along with the tops from the whole cloves (discard the stems), the peppercorns, cinnamon and oregano. Puree until completely smooth.
Heat the oil in a large casserole set over medium-high heat until very hot, but not smoking. Season the chicken with the salt and brown the chicken pieces for 2 to 3 minutes per side. You may need to do this in batches in order to not to crowd the casserole. Once you have removed all the chicken, immediately pour the tomato sauce into the hot oil and cover, as it will splatter. Reduce heat to medium.
Add a cup of chicken broth to the blender and puree for a few seconds to get all the remaining thick sauce out of the blender, pour into the simmering sauce and cover again. Cook for 10 minutes, stirring occasionally. Incorporate the remaining cup of chicken broth, almonds, raisins, olives and capers. Add the browned chicken pieces, cover and reduce heat to low and cook for 20 more minutes.
Remove the lid and add the pickled jalapeño slices. Increase heat to medium and cook for another 10 minutes, allowing all the flavors to blend and the sauce to thicken. Serve with rice.