In a medium-large pot, over medium heat, combine oil, garlic, and onions. Cook for one minute, until onions start to soften.
3. Step
Add celery and carrots, stir until onions are translucent.
4. Step
Add mushrooms, corn, parsley, tomato paste, thyme, sage, salt, and pepper until well mixed.
5. Step
Add veggie stock in half-cup (120 ml) increments, allowing it to come to a simmer before adding more.
6. Step
Add flour, then mix. Continue mixing until the mixture thickens.
7. Step
Once thick, remove from heat and pour into a pie dish.
8. Step
Add potatoes to a large pot and cover with lightly salted water. Set over medium-high heat and bring to a boil. Cook until potatoes have softened and are fork-tender.
9. Step
Remove from heat and drain.
10. Step
Mash potatoes then add butter, milk, salt, and pepper.
11. Step
Spoon potato mixture over the top of the veggies in the pie dish, and smooth so that it is evenly spread.
12. Step
Optional: Using a butter knife or a long, thin spatula. press into potato surface every inch (2 ½cm) to create a beautiful, undulating presentation.
