To the bowl of a crockpot add the onion, red pepper and garlic. Place the chicken on top. Measure out 2 cups of chicken broth in a separate bowl, add the tomato paste and apple butter. Whisk until combined. Add the mixture to the crockpot. Next add the beer, diced tomatoes, chili powder, cumin, smoked paprika, oregano, cayenne pepper, cocoa powder, salt and pepper. Lightly stir to combine. Cover and cook on high for 5 hours or on low for 7 to 9 hours. If the chili seems to thin remove the lid and let cook while you make the tostada chips.
About 30 minutes before you are ready to eat, preheat the oven to 475 degrees and place a rack in the top of the oven and one right below.
In a small bowl combine the brown sugar, chili powder and smoked paprika. Stir to combine. Line the corn tortillas in a single layer on 2 baking sheets. Spray with cooking spray or rub with olive oil and then generously sprinkle on the seasonings. Bake for 8 to 10 minutes, or until the tortillas are just beginning to turn golden brown. Rotate the pans (top goes below now) half way through. Remove from the oven and repeat with the remaining tortillas. Now take 4"chips" and spread each with a little shredded cheddar. Place back in the oven to melt for about 1 or 2 minutes, remove and top each cheesy chip with a non cheesy chip.
To assemble the stacks, place one plain tostada (meaning no melted cheese) on a plate, spread with cheese and then top with the hot chili. Now grab one of the cheesy chips and place it on top, top that chip with hot chili and them a sprinkle more of the cheese. Finally add one more plain chip, top with chili and more cheese. Repeat with the remaining chips, until you have four stacks. If desire, place the stacks on a baking sheet and melt the top layer of cheese. Top each stack with avocado, cilantro, jalapeños, a dollop of greek yogurt and Fritos if desired. Go to town!