Heat 1 teaspoon of olive oil in a small pan and once hot, add quarter of a chopped onion and diced carrot and stick of celery (optional). Cook for 8 minutes until softened, stirring occasionally. Stir in a teaspoon of harissa paste or a few dashes of Tabasco sauce and 150g passata or canned tomatoes. Simmer for 5 minutes and then stir in 200g butter beans canned and drained. Heat for another five minutes and serve sprinkled with chopped parsley (optional) and with a wholemeal roll or gluten-free alternative.