Heat a skillet over medium heat. Use the margarine or butter to spread on the two slices of bread. Layer the sandwich like this: bread, sharp cheddar, chicken, red onion, cilantro, BBQ sauce, smoked gouda, bread. Place the sandwich (butter side down) onto the hot skillet and use the back of the spatula to press the sandwich down gently. Let cook for 1 to 2 minutes or until the bread is nicely toasted. Use the spatula to carefully flip the sandwich over and toast for an additional 1 to 2 minutes. Cut in half and enjoy!