Roast the red pepper: Slice it in half and seed it, then place down on a foil lined baking sheet with the outside of the pepper up. Put under a broiler at 500 degrees for 8 minutes or until black charred and blistery.
Remove pepper from oven and wrap the foil that lined the baking sheet all around the pepper so that no steam can escape. Let it steam for about 10 minutes (out of the oven), this will help soften it and allow for easier peeling. After 10 minutes remove foil and peel the charred skin off the pepper and slice into strips.
While the pepper is broiling, heat oil in a saute pan, and once heated, add the butter. Then dash some garlic powder in the pan and stir.
Pound chicken breasts to about 1/2 inch of thickness and rub with salt and pepper.
Add chicken to saute pan once butter is melted. Cook for about 5-7 minutes on each side or until internal temperature reaches 165 degrees.
After pepper comes out of broiler, leave it on and place bread slices on a baking sheet. Broil until just crispy and a nice light brown color emerges. Then flip the bread, place the manchego cheese on half the slices, and put back under the broiler so the cheese melts and the other side of the bread gets toasty. Each side should only be a minute or two.
Make the garlic aioli by whisking all of the ingredients for it in a small bowl.
Spread garlic aioli on the non cheesed bread slices.
When chicken is cooked through, slice and place on the bread with the cheese. Top with slices of roasted red pepper and cover with other bread slice.