Watercress Poblano and Potato Soup

Heat oil and butter in a large saucepan over medium heat. When butter has melted, add onion and garlic. Stir frequently until onion is tender. Add potatoes, watercress, broth, water, corn and roasted poblano. Bring to a boil, reduce heat to medium low; simmer for 15 minutes. Reduce heat to low, season with salt and pepper. Stir in heavy whipping cream and blend using an immersion blender. You can use a regular blender by carefully blending in batches. Ladle into bowls, serve with Mexican crema, queso fresco and decorate with a watercress sprig.