Weekend Cooking; Vegetarian Sheperd's Pie

Sometimes I'm in need of comfort food, esp. during the cold months of the year. As I had some potatoes I wanted to use and I really love mashed potatoes (I'm one of those who can be content eating mashed potatoes straight out of the pot if I get the chance, am I the only one doing that?), I decided to make my version of Sheperd's Pie.

Sheperd's Pie
For the filling;
About 5 sping onions, chopped
250 g sliced mushrooms
4 dl mix of sweet corn, peas and carrots in equal size (in Norway you can buy a frozen blend called "Amerikansk blanding)
1 small can of tomato puré
4 dl stock
Salt and pepper
Garlic
1 tablespoon cornstarch
1 tablespoon butter

For the mashed potatoes;
Roughly 750-800g potatoes
Milk
Butter
Salt and pepper
Parsley and/or chives, chopped

Directions;
Pre-heat the oven to 200 degrees Celcius.

Boil the potatoes with a bit of salt until tender, add butter, milk and other seasonings and mash the potatoes. Add a bit more milk if needed.

In a pan, add butter, mushrooms and spring onions. When the mushrooms and onions are tender, add the rest of the ingredients and let it simmer until the potatoes are tender and you've made the mashed potatoes.

In an ovenproof dish, add first the veggie filling and then spread the mashed potatoes on top. Place the ovenproof dish in the pre-heated oven for roughly 20 minutes.