Heat up the oil in a saucepan and add onion, garlic, celery and carrot once hot
Fry for around 15 minutes until soft
Add the paprika, tinned tomatoes, cashew nuts, stock cube, oregano, salt + pepper and 600ml (2 ½ cups) water (and nutritional yeast and chilli if using)
Bring to the boil then turn down heat and simmer for around 20 minutes
Turn off heat and use a hand-held stick blender, food processor or blender to whizz until completely smooth - add more water if it's too thick, taste and adjust seasonings if necessary
Keeps well covered in the fridge for up to a few days and freezes well too