Turn the Instant Pot to saute, add in the oil, and let it heat briefly. Once heated, add the onions, carrots, and celery to the Instant Pot. Let saute for 2-3 minutes, or until the onions begin to soften. Add in the garlic and oregano. Saute that for 1 minute.
Add in dry red wine (or additional broth), scrape up any browned bits from the bottom of the inner pot, and let cook off for 1-2 minutes. Turn the saute function off by hitting cancel.
Add broth, zucchini, beans, elbow noodles, bay leaf, marinara, and salt, and stir to just combine.
Place the lid on the Instant Pot, be sure the venting knob is turned towards sealed or the lid is locked. Using the manual or pressure cook button, set the cooking time for 1 minute on high pressure.
Once the cooking time has elapsed, let the pressure release naturally for 10 minutes. After 10 minutes, do a quick release of the remaining pressure by using a wooden spoon to hit the vent knob from sealing to venting. (Be sure to stand away from the vent knob to protect yourself.)
Remove the bay leaf and then stir in the spinach and red wine vinegar. Place the lid back on the pressure cooker and allow the spinach to wilt for just a couple of minutes.
Serve the soup with freshly grated Parmesan if desired.
Wine: the dry red wine is optional but adds incredible flavor. Use a dry wine such as merlot or cabernet and be sure it is suitable for drinking. Don't use a wine labeled cooking wine, as the flavor is not very good!Beans: I use kidney beans and Great Northern beans, but you can use all kidney beans, white beans, or even garbanzo beans/chickpeas work great in Minestrone.Noodles: For the noodles, elbow or ditalini noodles are traditional, but orecchiette or small shells are a great substitute. Whole wheat or regular noodles work perfectly.Gluten-Free Modifications: For gluten-free noodles, I recommend Barilla Gluten Free--those are the only noodles that cook up well in the soup without releasing too much starch.Vegetable Options: Mix and match the vegetables in this soup. Besides zucchini, carrots, spinach, and celery, other great options include yellow frozen cut green beans, diced potatoes, diced sweet potatoes, or peas.In place of marinara: Use crushed tomatoes plus 1 teaspoon of Italian seasoning.Red Wine Vinegar: You can replace it with balsamic vinegar if needed. I don't recommend any other vinegar as a substitute. Spinach: If you want to use frozen chopped spinach, defrost it, squeeze out excess moisture, and add to the minestrone before pressure cooking. Or use kale, but add BEFORE pressure cooking. Storage: Leftover minestrone can be stored in a sealed container for up to 5 days in the refrigerator. It also can be frozen for up to 3 months. Keep in mind you may need to add a bit of stock when reheating, as the noodles will absorb the extra broth.