Peel the potatoes and cut into quarters. Place them into your varoma tray and basket and set aside until needed.
Cut the brown onion in half and place it into your Thermomix bowl. Add the garlic cloves and mix for 4 seconds, Speed 6.
Scrape down the sides of your Thermomix bowl and add the zucchini, carrot and celery pieces - which have all been cut into 4cm pieces. Mix for 5 seconds, Speed 6.
Scrape down the sides of your Thermomix bowl and add the olive oil. Cook for 4 minutes, Varoma temperature, Speed 2.
Add the crushed tomatoes water, lentils, vegetable stock paste and tomato paste.
Place the varoma into position and cook for 22 minutes, Varoma temperature, Speed 2, REVERSE.
In the meantime, preheat your oven and take out a 20cm square baking dish.
Check your potatoes, if they are not cooked all the way through, cook for a further 3 minutes or until tender.
Pour the lentil mixture into your baking dish.
Place the cheese into your Thermomix bowl and mix for 8 seconds, Speed 8 to grate. Transfer to a separate bowl and set aside until needed.
Without washing the bowl, insert the butterfly attachment and add the cooked potatoes, milk and butter.
Mix for 30 seconds, Speed 4 before scraping down the sides of your Thermomix bowl and mixing for a further 10 seconds, Speed 4.
Use a spoon to place the mashed potatoes on top of your lentil mixture and use a fork to cover.
Sprinkle with the grated cheese and place into the oven to bake for 30 - 35 minutes or until the cheese and potato are golden. Let the pie sit for 10 minutes before serving.