Roasted Garlic:Cut each head of garlic in half, horizontally, to split cloves down the middle. Place all six pieces on a sheet of aluminum foil and drizzle with the olive oil. Wrap the corners of the foil up and seal around garlic. Roast in the oven for 30- 40 min. until garlic is golden brown. Remove from the oven and open foil pouch to allow garlic to cool enough so that the cloves can be handled. When cool, gently squeeze heads of garlic until all roasted cloves pop out and reserve with the roasting oil for later use.
Assembly: In a 13X9X2″ dish or large sheet pan. Layer nachos, then bbq chicken, beans, tomatoes, red onion, and garlic cloves, topped with grated cheese.
BBQ Chicken: Season chicken breasts with salt and pepper. Grill until internal temperature reaches 165 degrees. Brush with BBQ sauce toward the end of cooking and add hot sauce if desired. Cool just long enough so chicken can be handled and cut into cubes. For saucier nachos, take grilled chicken and heat it in BBQ sauce on the stove for a few minutes.
Sprinkle with cilantro and repeat until all ingredients are used and the top layer ends with grated cheese and cilantro. Bake until cheese is melted and dollop surface with sour cream. Serve immediately.