Pre-heat a panini grill or george foreman grill. (can also be made in an oven if you dont have any of this equipment. Bake at 350 degrees for 6 - 8 minutes)
In a pot, add all sauce ingredients (crushed tomatoes, parmesan cheese, red pepper flakes, oregano) and cook on medium heat for 5 minutes or until it begins to bubble. Remove from heat.
Season the chicken with salt, black pepper, oregano, and paprika slightly rubbing seasoning into the meat.
Pre-heat a nonstick pan on medium/high heat and add tbsp of oil.
Cook the sliced chicken until no longer pink inside, about 6 - 8 minutes.
Layer the bread with asiago cheese and tomato sauce mixture using a spoon to spread evenly. Add chicken, spinach, and top with more asiago cheese.
Add the sandwich to the panini press or george forman and grill for 4 to 5 minutes.
Remove and cut the sandwich in half. Serve hot.