1) Fry the bacon and onion for a few minutes.
2) Add the rest of the veg, followed by the stock. Cover and simmer for 5-10 minutes.
3) Meanwhile, boil the potato and parsnip pieces until soft.
4) Drain, add the milk and cheese and mash it all up.
5) Mix the herbs into the pie filling and pour into a pie dish.
6) Spoon the mash on top and grill for 5-10 minutes to get a nice crispy top.