Fry the onions in oil in a large saucepan until translucent, add the vegetables and curry powder and briefly roast the tomato paste. Then deglaze with the vegetable stock, add the bay leaf and bring the stock to a boil. After about 5 minutes of cooking, add the lentils and cook for another 10 minutes. If the stew becomes too firm, add a little more vegetable stock. Finally, season with balsamic vinegar, ketchup and possibly a little pepper, salt and curry. Fish out the bay leaf.
Arrange the stew nicely on plates, e.g. with a dollop of sour cream and fresh parsley.
Serve with bread, e.g. pizza bread from the Alfredo.