- Combine tomatoes, butter, onion, 1/2 teaspoon kosher salt and pepper in a medium saucepan over medium heat. Bring to a gentle simmer and cook, uncovered, for about 45 minutes. As the sauce cooks, use a wooden spoon to break up the tomatoes and mash them into smaller pieces.
- Taste and add more salt or pepper as needed. Discard onion and blend smooth with an immersion blender.
Sauce can be kept, refrigerated, in an airtight container for up to 5 days.
- Preheat oven to 425°F. Line two baking sheets with foil and lay out eggplant slabs. Brush both sides with olive oil and season with salt and pepper. Bake for 20- 25 minutes, or until eggplants are tender and lightly browned. Set aside until cool enough to handle. Reduce oven temperature to 400°F.
- While eggplants cook, make ricotta filling. Combine ricotta, 3/4 cup parmesan, breadcrumbs, 1/2 teaspoon kosher salt, black pepper, basil, parsley and mint in a medium bowl. Mix until well combined.
- Spread a thin layer of tomato sauce in an 8-inch x 11-inch baking dish. Spoon about 2 tablespoons of ricotta filling onto the widest end of each eggplant slice. Roll the slices up tightly but gently, and place seam side down in a snug, even layer in the pan.
- Spoon more sauce over the eggplant rolls (you may not need all of it) and sprinkle with mozzarella and remaining 1/4 cup grated parmesan. Bake until cheese is melted and sauce is bubbly and fragrant, about 30 minutes. Serve hot.