Make the sauce. In a medium saucepan on low heat, add the butter, hot sauce, oregano and peppercorns. Steep on low until butter is melted and oregano is fragrant, about 20 minutes (be patient!). Strain out solids and reserve.
For the chicken, in a large bowl, mix together breast meat, half of the lime juice, half of the red onion and all of the garlic. Stir in the sauce and season with salt and pepper. Evenly spread the mixture in a 13 x 9-inch pan.
Make the guacamole. In a large bowl, mash the avocado with the ranch dressing and season with salt and pepper. Stir in the remaining lime juice and red onion, a big pinch of salt and several grinds of pepper.
With your hands (the best way to do it and avoid chip-breaking clumps) or a masher, mix and squish the ingredients until relatively smooth and only tiny chunks of avocado remain. Fold in the tomatoes and season with more salt, if needed. Spread the guacamole over the mixture in the pan. Top with the blue cheese and fried onions.
Serve at room temperature or slightly chilled with tortilla chips.
