Slice the eggplant into 1/4-inch thick slices. Season with salt and pepper, then brush both sides with olive oil.

Preheat the grill to medium-high heat. Grill the eggplant slices about 4 minutes per side until golden brown.

While the eggplant is grilling, slice the sandwich buns and spread 1 tablespoon of basil pesto on each side.

Assemble the sandwiches by placing grilled eggplant slices, mozzarella, and tomato slices on the bottom bun. Top with the other half of the bun.

Optionally, grill the assembled sandwiches for 2 minutes until cheese melts and bread is toasted.

Serve warm with a side salad or chips.