Creamy Mashed Potato and Leek Soup

Heat the oil in a large saucepan over medium-high heat. Add the leeks, fennel slices, and 1/4 teaspoon salt and cook, stirring occasionally, until soft, 8 to 10 minutes. Add the mashed potatoes and stock and simmer over medium heat, stirring occasionally, until completely warmed up, 4-6 minutes. Prepare the puree in a saucepan using a hand-held immersion blender (or, working in batches, in a standard blender). Pour on plates and sprinkle with fennel leaves. Serve with chips (if using). The Council: This soup goes well with other leftover vegetables. Try adding boiled carrots or parsnips before making the puree, or toss with the peas at the end.