Creamy Red Lentil and Sweet Potato Soup with Chard

1 T canola oil or butter
1 sm onion, diced
1 T curry paste
4 c stock (use vegetable stock if you prefer a vegetarian soup)
½ c split red lentils
1 lg sweet potato, peeled and cut into ½-inch pieces, or so
1 c milk
2 c chopped Swiss chard, spinach or kale
juice ¼ lemon (2 T)
kosher salt and fresh-cracked pepper
plain yogurt for serving (optional)

Cook the onion in the oil over medium low heat in a large pot until starting to colour. Add the curry paste and cook for 1 minute. Add the stock and bring to a boil. Add the sweet potato, reduce heat and simmer covered for about 5 minutes. Add the lentils and continue to simmer covered for about 10 minutes until the lentils and sweet potatoes are tender. Add the milk slowly to the hot soup. You could leave the soup chunky, blitz a portion of it or purée all of it for a smooth consistency. Add the greens and stir until wilted, about 1 to 2 minutes (if using kale it might take longer). Squeeze in the lemon juice and check for seasoning. Serve with yogurt if using. Serves 4-6.