Use 1 cup chopped cauliflower, 2 carrots, 2 celery ribs and 1/2 to 1 cup of olives (from the jar), all thinly sliced or chopped. Oil (and Vinegar, if desired). Use 1 cup of good quality olive oil and 1 cup of white wine vinegar. Some Chicago style giardiniera brands use only oil. If you prefer no vinegar, replace it with water or more oil.
Chicago Giardiniera is mostly serrano peppers and it should be the main ingredient. The flavor however is not just hot pepper, it is rich with oil and olives, a little hint of sweetness from the red bell peppers and carrots, some brightness from the vinegar and a touch of garlic and oregano. It is so much more than just spicy!
I have seen recipes claiming to be Chicago Giardiniera with a total of 6 hot peppers in it. I promise you that is not at all what Chicago Giardiniera is like. Chicago Giardiniera is mostly serrano peppers and it should be the main ingredient.
The serving size in the nutritional info is ¼ cup giardiniera. After the 24 hour period, you may keep the giardiniera in the large container, or portion into smaller jars. It will last 2-3 weeks covered in the refrigerator. When storing the giardiniera, make sure the oil and vinegar covers the vegetables completely.