This hearty soup can be cooked on the stove or in an Instant Pot. I always cook it in the Instant Pot because it makes it so easy. You just add the ingredients, set the timer and leave it. After the cooking time has finished the Instant Pot will turn off, and it can keep the soup warm for you for several hours. I love coming home to a ready-to-eat meal.
Here is a link to the Instant Pot that I have (I have and recommend the 8 litre): Instant Pot 8 litre on Amazon (This is an affiliate link).
2 onions, finely diced
3 sticks celery
3-4 medium potatoes, diced
1/3 cup pearl barley
1/2 cup red lentils
1/2 cup split peas
1/4 cup brown or black lentils
9 cups water
400g can condensed tomato soup OR 400g can chopped tomatoes OR 1/3 cup tomato paste
1 cup corn kernels
2-3 tablespoons vegetable stock powder
Salt and pepper, to taste
Stove Top Method
Optional: Soak the barley and split peas for at least four hours in plenty of water. (This will reduce cooking time). Drain and add to a large soup pot.
Add the remaining ingredients and bring to a boil.
Simmer for 30 minutes (if soaked) or 45 minutes (if not soaked), stirring occasionally, or until the barley and split peas are cooked.
Pressure Cooker Method
Add all the ingredients to an 8 litre Instant Pot and set the lid in place. Set the Instant Pot to pressure cook for 20 minutes.
At the end of cooking, allow the pressure to drop naturally for 15 minutes (or longer if you're not home), then release remaining pressure manually.