Broiled eggplant stands in for lasagna noodles in this robust dish.
- Trim eggplants, but leave peel on; slice lengthwise ¼-inch to 1/3-inch thick. Layer in a colander, salting each layer. Let stand in the sink or over a bowl for 15 minutes to drain bitter juices.
- Meanwhile, in a heavy medium skillet over medium heat, cook beef, breaking it up with a wooden spoon until browned and beginning to crisp, about 6 minutes. Drain liquid from skillet and stir in tomato sauce. Remove from heat; set aside to cool.
- Brush mushrooms lightly with olive oil; season with salt and pepper. Cook 4 minutes per side in a large skillet over medium heat until lightly browned. Cut into 1/2-inch slices; set aside.
- Heat broiler. Pat eggplant dry. Brush olive oil on both sides. Broil 3 minutes per side until just beginning to char; set aside to cool slightly. Reduce oven temperature to 400°F.
- In a food processor fitted with a metal blade, combine ricotta, spinach, eggs and Parmesan cheese. Pulse until blended. Add pepper.
- Lightly oil a 13- by 9-inch glass baking dish. Arrange half the eggplant slices in an even layer, overlapping slightly. Top with half the mozzarella and all the mushrooms. Spoon on half the meat sauce, then spread all the ricotta mixture, in an even layer. Top with the remaining eggplant, followed by the remaining sauce and the mozzarella.
- Bake about 20 minutes, until cheese is melted and sauce is bubbly. Let cool slightly before cutting and serving.