Vegetarian pot pie

medium Yukon gold potatoes

olive oil (divided use)

large onion (finely chopped)

medium carrots (peeled and sliced ¼-inch thick (about 1 ½ cups))

unsalted butter

unbleached all-purpose flour

milk

vegetable broth

kosher salt

freshly ground black pepper

dried thyme

white wine like Snoqualmie Chardonnay or Sauvignon Blanc

frozen peas (thawed)

sheet puff pastry (thawed and unfolded)