Prepare all the veggies by finely chopping them in a food processor or by hand and putting to one side.
Take cavolo nero leaves off the stalks and roughly chop/slice.
Heat tablespoon of oil in a lidded non-stick pan or cast-iron casserole and fry vegan sausages until nice and brown. Take sausages out onto a plate.
Add remaining tablespoon of oil to the pan followed by all the chopped veggies and sautée them stirring frequently until they start to soften, approximately 5-8 min.
Add dried herbs, vinegar, dried and rinsed lentils, passata and stock and stir well. Season to taste.
Bring to boil, turn down the heat and simmer, covered until lentils are tender (approximately 30 min) stirring occasionally. You might have to add splash of water or stock if they get too dry.
You can either cook cavolo nero separately and stir it into the final dish or add it after about 20 minutes into cooking your lentils to cook in a casserole.
Add mustard and stir it in.
Once lentils are cooked and cavolo nero has softened add back your cooked vegan sausages for 5 minutes to warm them up.
Garnish your vegan sausage casserole with some fresh thyme or chopped parsley and enjoy!