First, make the chipotle chicken. Add sliced chicken to a small frying pan and season with chipotle powder, paprika, garlic powder, onion powder, and salt. Cook over medium-high heat until cooked through, about 6 to 8 minutes, stirring occasionally.
Transfer cooked chicken to a small bowl and set aside. Add vegetable oil to the frying pan, lower heat to medium, and add sliced bell pepper and onion. Sauté until vegetables are slightly softened, about 2 to 3 minutes, then remove from heat.
Preheat a cast iron griddle over medium-low heat. Spread 1 teaspoon butter on the outside of each slice of sourdough bread, then spread 1 teaspoon chipotle mayo on the inside of each slice of bread.
Assemble the chipotle chicken melt. Place one slice of bread butter side down (chipotle mayo side up) on the griddle. Top with one slice of pepper jack cheese, then add the cooked chipotle chicken, then the peppers and onions. Top with remaining slice of cheese and close the sandwich with the other slice of bread, chipotle mayo side down.
Cook until the bottom turns golden brown and the cheese is melted, about 3 to 4 minutes, then carefully flip the sandwich and cook until the bottom is golden brown, another 3 to 4 minutes. Optionally, you can use a preheated cast iron grill press on top of the sandwich to cook from both sides at the same time and avoid flipping the sandwich.
Transfer chipotle chicken melt to a cutting board, slice in half, and serve immediately.
Notes
Chipotle chicken: This recipe details how to cook a small batch of seasoned chipotle chicken using raw chicken tenders. However, you can simply reheat and season plain, pre-cooked chicken as an easy shortcut! Using shredded rotisserie chicken or thinly sliced plain grilled chicken, simply reheat in a frying pan over medium heat with the seasonings listed above. You may want to add a bit of vegetable oil to the chicken to help the seasonings stick.Sourdough bread: A high-quality sourdough bread fresh from the bakery will make all the difference in this sandwich!Chipotle mayo: You can try our original recipe for chipotle mayo here - we use it all the time now instead of buying it from the store. All you need is light mayo and a few seasonings to make this delicious homemade condiment!Cast iron grillpress: If you want to avoid flipping melts, paninis, and other thick grilled sandwiches like this chipotle chicken melt, you can try cooking them with a cast iron grill press. Just get it plenty hot ahead of time, and use it to press down on the top of your sandwich as it cooks so you can crisp both sides at once.