For the potatoes:
1. Place the potatoes and garlic in a saucepan, cover them with water and add a pinch of salt. Bring to a boil and simmer until the potatoes are tender, about 20 minutes. Drain and mash the potatoes and garlic. Stir in the milk and season to taste with salt and pepper.
For the vegetables:
1. In a large soup pot, heat the olive oil over medium heat. Add the onion and mushrooms and cook until the vegetables are soft.
2. Stir in the flour and cook for 2 minutes more.
3. Slowly whisk in the vegetable broth. Bring the mixture to a boil, add the frozen vegetables and simmer for 3 minutes. Season the vegetable mixture with salt and pepper.
4. Pour the vegetables into a casserole dish. Spread the mashed potatoes over the vegetable mixture. Place the dish on a cookie sheet and bake for 30 minutes or until the potatoes are lightly browned.
5. Serve hot.Serving Size: 1 piece