In a large pot, heat oil on medium. Add onions and salt. Sweat until onions soften (about 10 minutes) stirring often, to prevent browning.

Hold diced potato in a bowl covered with water to prevent browning. When onions are soft, add the stock, corn kernels, and potato. Cover with lid and bring to a boil (10 minutes). Look for steam to signal when to lower the heat. Continue to simmer on medium to medium-low heat for 20 minutes with the lid slightly ajar.

Puree in batches in a high speed blender until silky smooth. You can reserve some of the vegetables and add it back to the soup to keep some of the texture. Serve with red pepper coulis and garnish with onion sprouts if you can find them.