Start by making the mashed potatoes by adding them peeled and chopped potatoes to a large pan, covering with water, bringing to the boil and allowing to simmer for about 15 minutes or until soft enough to mash. Drain the potatoes then return them to the pan, add the milk, oil and salt and mash until silky smooth and fluffy. Leave to one-side while you prepare the filling.
Add the oil to a large pan which has a lid and turn up the heat to a medium setting. Add the chopped onion and place on the lid. Leave to cook for about 3 minutes before adding the pepper and cubed butternut squash. Secure the lid and leave to cook on a low heat for 15 minutes until they begin to soften.
After 15 minutes, add the drained black beans, tomatoes, vegetable boullion powder, thyme, mustard, cinnamon and sugar. Then stir through the water until well incorporated.
Finally, add the kale and stir through.
Pour the vegetable mixture into a suitable oven proof dish (mine is oval and measures approx. 30cm at it widest point).
Scatter the sliced garlic cloves evenly through the filling.
Now spoon on the mashed potato, then use a fork to spread out over the filling until no gaps remain. Use a fork to create lots of little peaks in the potato which will create a lovely crunchy topping during baking.
Cook the dish in a 180 degree pre-heated oven for 45 minutes. To crisp the topping more, place the pie under the grill (check your oven proof dish allows for this without cracking) and grill to your liking.
Scatter with fresh thyme (optional) before serving.
Serve with steamed broccoli.