Preheat the oven to 350°F and line a baking sheet with parchment paper.
Arrange the diced eggplant on the baking sheet and drizzle the pieces with olive oil. Use your hands to rub the oil all over the eggplant pieces.
Place the baking sheet into the oven and bake the eggplant for about 30 minutes, until the pieces are browned and tender, flipping them about halfway through.
While the eggplant roasts, place all ingredients for the dressing into a blender. Blend until smooth. Give the dressing a taste-test and adjust any seasonings to suit your taste.
To prepare the walnuts, first stir them together with the soy sauce in a small bowl, until they're evenly coated. Arrange them on a baking sheet, then place the baking sheet into the oven with the eggplant.
Roast the walnuts for about five minutes, until they darken slightly. Remove them from the oven when they're done and place the baking sheet on a cooling rack.
Once the eggplant comes out of the oven, transfer it to a medium bowl and add about two tablespoons of the dressing. Stir the eggplant up to coat it in dressing.
Assemble the salad. Arrange the spring mix, bell pepper, cherry tomatoes, avocado and basil in a large bowl. Add the eggplant and walnuts, then drizzle the salad with dressing, using only as much as you like (Note 1). Toss the salad and sprinkle it with salt and pepper to taste.
Serve.