Heat 2 tbsp olive oil in a large saucepan.
Add a chopped onion onion and three chopped stalks of celery. Stir well. Cover with a lid, reduce the heat to low and cook for five minutes. Add 2 chopped carrots, stir again, cover and cook for a further 10 minutes until the vegetables are starting to soften.
Add 2 cloves chopped garlic, 1 tsp fennel seeds and thyme leaves (picked and chopped from 3-4 sprigs of thyme), stir and cook for a minute or two.
Pour in a tin of borlotti beans and 1 litre vegetable stock. This makes quite a liquid soup - if you prefer yours thicker perhaps start with 500ml and add water until you have your preferred consistency. Bring to the boil, then cook for 15 minutes or until all the vegetables are cooked through.
Stir through 100g baby spinach leaves until wilted.
Season with salt, pepper and chilli flakes to taste.