In large soup pot over medium heat add 2 tablespoons olive oil and sauté the onion until it is translucent. Add the minced garlic and sauté one more minute. Add the salt and pepper. Add the chard stems, kale stems, potato and carrot. Sauté 5 minutes to soften the vegetables and bring out the flavors. Add 1/2 cup of stock, cover the pot and cook for 10 minutes.