Peel and finely chop the onions and garlic, and finely slice the carrot and parsnip. Cut the fine beans into bite-size pieces. Drain the lentils and rinse thoroughly. Put the oil into a large pan on a high heat, add the onions and garlic and cook 2 minutes, stirring regularly.
Add the drained lentils to the pan, along the chopped tomatoes, black pepper, smoke paprika, bay leaves, maple syrup and tamari. Bring to the boil, then lower the heat and add the fine beans and parsley (roughly chopped) for some colour. Leave to simmer, checking from time to time that the mixture is not sticking to the pan. Continue to simmer while the potatoes cook, stirring occasionally to ensure nothing sticks to the pan.
Preheat over to 200°C/400°F/Gas Mark 6.
While the filling is simmering, chop the potatoes evenly into small bite-size pieces and put them into a medium pot (we usually leave the skins on). Cover with boiling water, bring back to the boil, then reduce the heat and leave to simmer until tender (about 15 minutes). Drain the potatoes, return them to the pot and mash with a potato masher, adding the oil and non-dairy milk a little at a time until your mash reaches the right texture (smooth but not sloppy). Taste and season with salt and pepper.
Tip the lentil mixture into a lasagne-type casserole dish and top with the mashed potato (aim for approximately half the lentil and half the potato). Bake in the preheated over for 20-30 minutes, until the top of the potato is turning golden and starting to crisp. Remove from the oven and serve.