Preheat panini press:

Should you be employing an electric panini press, warm it to your preferred heat level.

Butter bread slices:

Apply a thin layer of butter to one face of each bread slice.

Assemble sandwiches:

Place the buttered side downward on four bread slices. Layer chicken, mozzarella, tomato slices, balsamic glaze, and basil on top. Cover with the remaining bread slices, buttered side facing up.

Heat pan or skillet:

If you are using a panini pan or a skillet, warm it over a medium-high flame.

Cook paninis:

After it's hot, put the sandwiches in the pan (or press) and lower the press. Cook for 1-2 minutes, keeping a close watch, until they turn golden. Turn them over and cook the opposite side. When using an electric press, flipping is unnecessary.

Slice and serve:

Slice the paninis in half if you like, and serve while hot.