I am quite generous with the measurements of the ingredients when I make this myself.
There are a variety of ways to remove the bitterness from eggplant. Tempering Bitter Eggplant. When I prepare the eggplant I slice it into 1/2 inch slices, lay the slices on paper towels and salt the slices generously and evenly. I do this about an hour in advance of using it. Be sure to rinse the slices and pat them dry. I then dice them.
Chop all of your vegetable approximately the same size so that they will cook evenly.