Ingredient amounts will vary depending on the size of your eggplant. I used a two pound eggplant for this recipe. Select a baking dish that will be large enough to hold the sliced eggplant in a single layer of overlapping pieces. 9X13 is a good size for a large eggplant.

Prep the eggplant: Preheat oven to 375°F. Slice unpeeled eggplant into ¼-inch rounds. Arrange on a paper towel–lined baking sheet, sprinkle lightly with kosher salt, cover with more paper towels, and top with another baking sheet plus something heavy. Let sit 15 minutes, then discard paper towels.

Toast breadcrumbs: Heat 1 Tbsp olive oil in a skillet, add panko, and stir until golden. Transfer to a bowl to cool. Stir in parmesan once cooled.

Bake eggplant: Drizzle 2 Tbsp olive oil over a baking sheet and spread evenly. Arrange eggplant slices, flipping once to coat both sides. Use a second sheet if needed. Bake 10 minutes, until lightly colored but not fully cooked.

Assemble gratin: Spread a thin layer of sauce in the bottom of your casserole dish. Starting at one end, arrange the eggplant slices in a slightly overlapping row, like shingles on a roof, until you reach the other side. Spoon a little more sauce over the slices, then scatter on some mozzarella. Repeat with more rows of eggplant, sauce, and cheese until the dish is full.

Top and bake: Sprinkle parmesan-breadcrumb mixture evenly over top. Bake uncovered 20–25 minutes, until bubbly and golden.

*Rest 5 minutes before serving. Garnish with fresh herbs if desired.