01 - Butter one side of each bread slice generously.
02 - Place two bread slices butter-side down on your work surface.
03 - Spread 1 tablespoon of basil pesto onto the unbuttered side of each of these two bread slices.
04 - Distribute the sliced fresh mozzarella evenly over the pesto.
05 - Top each assembly with the remaining bread slices, ensuring the buttered side faces up.
06 - Heat a non-stick skillet over medium heat until warm.
07 - Carefully place the assembled sandwiches into the hot skillet. Cook for approximately 3 to 4 minutes per side, or until the bread achieves a deep golden-brown hue and is delightfully crisp. Gently press down with a spatula for uniform browning and optimal cheese melt.
08 - Remove the grilled sandwiches from the skillet. Allow them to rest for 1 minute before slicing diagonally and serving immediately.