This cottage pie recipe is fantastic. I usually replace the celery with other veggies - peas, courgettes, mushrooms. I make it about once a week as my toddler loves it - sweet potato also works a charm instead of potato.
This went down a treat. At first I thought I was pushing it with spring onion and mustard but neither overpowered the dish. It's worth getting Maris Piper potatoes instead of plain white potatoes for a lovely fluffy topping. Real comfort food and a blast of Omega 3 too.