While the tomatoes are roasting, prepare the terrine ingredients.
If you prefer to remove the skin from the eggplant, do so, but this is not a necessary step. Season both sides of the eggplant slices.
In a large skillet, heat 2 tablespoons olive oil on medium-high heat until hot. Turn heat down to medium. Place the eggplant in batches, and cook until browned. Set aside. Peel leeks apart into layers of 2-3 layers per layer of terrine. Cook the leeks in the same manner as the eggplant, and reserve.
Seed and slice the peppers into thick slices vertically. Place in a baking pan with oil sprayed onto the bottom or some olive oil brushed on the bottom, and broil skin side up until skin is charred. Remove skin and reserve peppers.
Line a loaf pan with plastic wrap going both vertically and horizontally, and leave excess for wrapping terrine over the pan edges by 5-6 inches on each side. Assemble the terrine ingredients.
What is important is that the ingredients are going in the same direction because it’s the layers that are seen and in part what keeps the terrine together. Lay a layer of eggplant at the bottom of plastic wrap-lined loaf pan, followed by a layer of leeks, followed by feta cheese, followed by basil leaves. (The assembly process takes only a few minutes.) Layer and repeat until ingredients are used up, ensuring that the final layer is eggplant.
Finish wrapping the plastic wrap around the terrine. Press the layers together. Lay some weight on the terrine, and place in refrigerator for at least 4 hours or overnight if possible.
For serving, carefully remove terrine from loaf pan. Remove wrap from terrine, and with a very sharp knife, slice. Place a pool of cooled sauce on plate and top with terrine. Serve.