For the cheese sauce: Combine 8 ounces of the beer, the Chicken Seasoning Blend and the chipotle steak seasoning in a saucepan over medium heat and bring to a simmer. Gradually whisk in the cheese; cook just until the cheese is melted, adding more beer if the sauce is too thick. Keep warm.
For the chicken: Heat a cast-iron griddle over medium-high heat. Add 1 tablespoon of the olive oil and the onions and cook for 3 to 5 minutes. Add the chicken, drizzle with the remaining tablespoon olive oil and sprinkle with the Chicken Seasoning Blend. Cook until the chicken is browned, 5 to 8 minutes. Pour the chicken stock over the chicken and cook for another minute.
To build sandwiches: Coat the bottom half of each hoagie roll with mayonnaise. Divide the chicken and onions among the rolls. Drizzle with cheese sauce and top with a bit of relish.
Chicken Seasoning Blend:
In a small bowl combine the chicken seasoning, kosher salt, garlic salt and a few grinds of black pepper.