Slice your chicken breasts in half horizontally to make 4 thin chicken cutlets. Coat in flour, followed by egg wash, followed by panko breadcrumbs. Repeat for all 4 cutlets. Place a pan on medium heat with a drizzle of olive oil and fry the cutlets for 4 minutes on each side until golden.
Meanwhile, make your romesco sauce by combining all your romesco ingredients into a blender. Blend until smooth (add more olive oil if it's not blending smoothly) and then set aside.
Remove your fried panko chicken from the pan once golden and crispy. Set aside on a plate with a sheet of kitchen towel underneath to absorb any excess oil.
In a bowl, combine the sour cream, mayonnaise, lemon juice, grated parmesan, and black pepper. Drop in your lettuce and rocket and combine.
Turn on the grill. In a small bowl, combine the butter, garlic, and parsley for your butter mixture. Slice your focaccia breads in half and divide the butter mixture evenly between the halves, spreading the butter on each side of the focaccia slice (top and bottom). Grate parmesan onto the buttered focaccia until covered. Place the focaccia on trays and place under the grill for a few minutes until bubbling and slightly golden. Remove from the grill.
Time to layer up your sandwich!! So place down a dollop of the romesco sauce on each side of the focaccia. Then on the bottom slice of the focaccia, add on your chicken cutlets, salad, and then the top slice of focaccia. Repeat for the other sandwich.
Wrap your focaccia sandwiches in baking parchment and then either eat straight away or store in the fridge until you're ready to go!