01 - In a medium mixing bowl, thoroughly combine grated cheddar, cream cheese, mayonnaise, chopped pimentos, garlic powder, smoked paprika, cayenne pepper (if desired), salt, and black pepper until smooth and homogeneous.
02 - Arrange bread slices on a work surface. Evenly spread pimento cheese mixture onto 4 slices, then top each with a remaining slice to create sandwiches.
03 - Generously spread softened butter on the exterior sides of each sandwich.
04 - Heat a large skillet or griddle over medium heat until hot.
05 - Place prepared sandwiches onto the skillet. Cook for 3 to 4 minutes per side, pressing gently, until bread is crisp and golden brown and cheese filling has melted.
06 - Remove sandwiches from the pan, allow to cool briefly, slice with a bread knife, and serve immediately while warm.