Vegetable Shepherd's Pie with Sweet Potato

First, peel the potatoes and sweet potatoes, cut them into cubes, then place them in a large pot. Pour enough water to cover them and bring to a boil. Meanwhile, peel the red onion and garlic; finely chop the onion and crush the garlic. When the water starts to boil, reduce the heat and cook the potatoes until tender, for about 15-20 minutes.

Meanwhile, clean the mushrooms and cut them into small pieces (about bean-sized). Drain the red beans and lentils, then rinse them with cold water.

Once the potatoes are tender, drain them, add the milk and salt, then mash them into a smooth, creamy puree.