Prepare the Crust:

In a large bowl, mix together flour and salt. Add the butter and use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.

Gradually add ice water, stirring until the dough comes together. Wrap in plastic and refrigerate for at least 1 hour.

Make the Filling:

Heat olive oil in a large skillet over medium heat. Add onion and garlic, cooking until softened.

Add carrots, parsnips, butternut squash, and Brussels sprouts. Cook for about 10 minutes, or until vegetables start to soften.

Stir in peas, corn, thyme, rosemary, salt, and pepper.

Sprinkle flour over the vegetables, stir, and cook for 2 minutes.

Slowly add vegetable broth, stirring continuously. Bring to a simmer and let cook until the sauce thickens.

Stir in heavy cream or coconut milk, adjust seasoning, and remove from heat.

Assemble and Bake:

Preheat your oven to 375°F (190°C).

Roll out the pie crust on a floured surface to fit your pie dish.

Pour the vegetable filling into the pie dish.

Place the crust over the filling, trim any excess, and crimp the edges. Make a few slits in the top to allow steam to escape.

Bake for 35-40 minutes, or until the crust is golden brown.

Let cool for a few minutes before serving.