Every international kitchen has one or more dishes in its arsenal that you could call waste dishes. Pizza, Irish stew, bread pudding, bean soup, lasagna, stew, tripe, paella. These are all originally dishes where the leftovers are turned into a dish. Born from poverty, frugality, respect for food, or a combination of the three. These days, creating dishes in which you process the leftovers in your refrigerator is usually out of respect for food, laziness to walk to the store or still out of poverty.
With basics as a starting point (broth, rice, pasta, potato) and what is in your refrigerator (or what you can buy in season), you can create a wide variety of dishes in combination with pepper, salt and spices. Good for your stomach, your mood and the planet.