Vegetarian Pastitsio

Name: Vegetarian Pastitsio
Ingredients: 1 1⁄2 cups cooked lentils (I'd use brown); 3 tablespoons olive oil; 3 tablespoons butter; 2 onions, finely chopped; 1 large eggplant, chopped into small pieces (unpeeled); 1 -2 garlic clove, minced; 1⁄2-1 teaspoon cinnamon; 1⁄2-1 teaspoon oregano; salt and pepper, to taste; 8 medium tomatoes, peeled and chopped or 1 (32 ounce) can chopped tomatoes, drained; 8 ounces tomato paste; 1⁄2-1 cup parmesan cheese, grated; 16 ounces cooked macaroni; Custard Sauce; 3 cups milk, heated; 3 eggs, beaten; 3 tablespoons flour