Melt the butter and oil in a large pan over a medium heat.
Add the onion, celery, carrot, garlic and sweat for 10 minutes until softening.
Add the sage, thyme and coriander and cook for another 2 minutes,
Stir in the gravy granules, cooked brown lentils, tinned tomatoes and 250ml (1 cup) boiling water.
Bring up to the boil, then reduce to a simmer for 20 minutes.
Make the mashed potato topping
While your filling is simmering, put the potatoes in a large pan of water, bring to the boil. Simmer for 10-15 minutes until a butter knife slides into one easily.
When your potatoes are done, drain them, return them to the pan, the mash or rice until smooth.
Add the butter and milk, stir and season to taste.
Assemble your vegetarian shepherd’s pie
Preheat your oven to 200C (180C fan / 390F).
Grease your roasting tray and add the cooked filling.
Spoon or pipe the potato over the top of the filling.