Directions to make split pea and barley soup. Remove the spice packet. Heat 2 tablespoons of olive oil in a soup pot. Dice 1 onion, 2 carrots, and 3 celery ribs and add them to the pot. Once they smell fragrant, add the split peas and barley. Add the spice packet and 2 quarts of water and bring to a boil over high heat. Reduce the heat to medium-low, cover, and simmer for 40-45 minutes, until the barley plumps and the split peas soften (depending on the freshness of your peas and barley, you may need a splash more water). Taste and adjust seasoning to taste (a splash of lemon juice or red wine vinegar is always nice in soup). Serve chunky or puree smooth.